JP2019145201A - Secondary cell - Google Patents

Abstract

To provide a secondary cell which allows for efficient installation of an electronic medium having flexure shape.SOLUTION: In a secondary cell 100 where an electrode assembly, including a positive electrode, a negative electrode and a separator placed between the positive and negative electrodes, and an electrolyte are received in an exterior body, a concave surface 11 recessed in the inside direction is formed in a part of the contour face 10 of a secondary battery 100, and a curved surface 12 is formed in at least a part the concave surface 11. Bending angle θ of the curved surface 12 is 90-180° with the flexure center point C as the index point, and the flexure center point C indicates a point that is equidistance from any of one end of the curved surface 12, the other end of the curved surface 12, and the midpoint of one and the other ends in the curved surface 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a secondary battery.

  Secondary batteries that can be repeatedly charged and discharged have been used for various purposes. For example, the secondary battery is used as a power source for electronic devices such as smartphones and notebook computers.

  In recent years, there has been an increasing demand for thinner and smaller electronic devices, and accordingly, it is required to efficiently install electronic media (electronic components, etc.) in secondary batteries within the electronic devices. Yes. In this regard, Patent Document 1 discloses a secondary battery provided with a recessed region having a bent shape.

Japanese Patent Laying-Open No. 2015-536036

  However, the inventors of the present application have found that the following problems may occur when using a secondary battery having a recessed region in a bent form. Specifically, the shape of the electronic medium connected to the secondary battery may be a curved shape depending on the application. In this case, since the shape of the recessed area of the secondary battery is different from the shape of the electronic medium, a curved electronic medium is provided so as to be fitted into the recessed area of the secondary battery due to the difference in shape. It becomes difficult. Therefore, it does not appropriately respond to a request for efficient installation of an electronic medium for a secondary battery in an electronic device.

  An object of this invention is to provide the secondary battery which enables the efficient installation of the electronic medium which has a curved shape.

In order to achieve the above object, in the present invention,
An electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and an electrolyte, and a secondary battery in which an electrolyte is housed,
A concave surface that is recessed inwardly is formed on a part of the contour surface of the secondary battery, and a curved surface is formed on at least a part of the concave surface, and the curved angle of the curved surface is based on the curved center point 90 degrees or more and 180 degrees or less, and the bending center point is a point that is equidistant from one end of the curved surface, the other end of the curved surface, and an intermediate point between one end and the other end of the curved surface. A secondary battery is provided.

  According to the secondary battery of the present invention, it is possible to efficiently install an electronic medium having a curved shape.

FIG. 1 shows a schematic plan (side) view of a secondary battery according to an embodiment of the present invention. FIG. 2 shows a schematic plan view (side surface) of a secondary battery having a curved surface with a curved angle of 90 °. FIG. 3 shows a schematic plan (side) view of a secondary battery having a curved surface with a curved angle of 120 °. FIG. 4 shows a schematic plan (side) view of a secondary battery having a curved surface with a curved angle of 180 °. FIG. 5 shows a schematic plan (side) view of a secondary battery in which a curved surface is formed on a part of the concave surface. FIG. 6 is a schematic plan view (side view) showing a state in which two secondary batteries are arranged so that curved surfaces face each other. FIG. 7 shows a schematic diagram illustrating the concept of the curvature center point.

  Hereinafter, a secondary battery according to an embodiment of the present invention will be described. First, before describing the “characteristic part” of the secondary battery according to the embodiment of the present invention, the configuration of the secondary battery according to the embodiment of the present invention will be described.

[Configuration of Secondary Battery of the Present Invention]
A secondary battery according to an embodiment of the present invention has a structure in which an electrode assembly and an electrolyte are accommodated and enclosed in an exterior body. The electrode assembly includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. There are roughly two types of electrode assemblies. In the first type, the electrode assembly has a planar laminated structure in which a plurality of unit electrode units including a positive electrode, a negative electrode, and a separator are laminated. In the second type, the electrode assembly has a winding structure in which an electrode unit including a positive electrode, a negative electrode, and a separator is wound in a roll shape. In addition, a spacer is provided in the exterior body in order to prevent electronic contact between the positive and negative electrodes and the exterior body. The positive electrode is electronically connected to the positive electrode external terminal via the positive electrode current collecting lead. The external terminal for positive electrode is fixed to the exterior body by a seal portion, and the seal portion prevents electrolyte leakage. Similarly, the negative electrode is electronically connected to the negative electrode external terminal via the negative electrode current collecting lead. The external terminal for negative electrode is fixed to the exterior body by a seal portion, and the seal portion prevents electrolyte leakage.

  The positive electrode is composed of at least a positive electrode material layer and a positive electrode current collector, and the positive electrode material layer is provided on at least one surface of the positive electrode current collector. The positive electrode material layer contains a positive electrode active material as an electrode active material. The negative electrode is composed of at least a negative electrode material layer and a negative electrode current collector, and the negative electrode material layer is provided on at least one surface of the negative electrode current collector. The negative electrode material layer contains a negative electrode active material as an electrode active material.

  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 are materials directly involved in the transfer of electrons in the secondary battery, and are the main materials of the positive and negative electrodes that are 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, a secondary battery in which lithium ions move between the positive electrode and the negative electrode through the electrolyte to charge and discharge the battery is preferable. When lithium ions are involved in charging / discharging, the secondary battery according to this embodiment corresponds to a so-called “lithium ion battery”.

  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, facilitating the transfer of electrons that promote the battery reaction. Therefore, a conductive additive 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 mixture layer” and “negative electrode mixture 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, such a lithium transition metal composite oxide is preferably included as the positive electrode active material in the positive electrode material layer of the secondary battery. 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. In a more preferred embodiment, the positive electrode active material contained in the positive electrode material layer is lithium cobalt oxide.

  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 contained 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, copper, nickel, aluminum, silver, etc. And at least one selected from metal powders, polyphenylene derivatives, and the like. In a more preferred aspect, the binder of the positive electrode material layer is polyvinylidene fluoride, and in another more preferred aspect, the conductive additive of the positive electrode material layer is carbon black. In a more preferred embodiment, the binder and conductive additive of the positive electrode material layer are 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, 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. In a more preferred embodiment, the negative electrode active material of the negative electrode material layer is artificial graphite.

  The binder that can be included in the negative electrode material layer is not particularly limited, and may include at least one selected from the group consisting of styrene butadiene rubber, polyvinylidene fluoride, polyimide resin, and polyamideimide resin. it can. In a more preferred embodiment, the binder contained in the negative electrode material layer is 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, copper, nickel, aluminum, silver, etc. And at least one selected from metal powders, polyphenylene derivatives, and the like. 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.

  In a more preferred embodiment, the negative electrode active material and the binder in the negative electrode material layer are 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 is a member provided from the viewpoints of preventing short circuit due to contact between the positive and negative electrodes 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 electrolyte assists the movement of metal ions released from the electrodes (positive electrode / negative electrode). The electrolyte may be an electrolyte containing a “non-aqueous” solvent such as an organic electrolyte and an organic solvent and a solute, or may be an “aqueous” electrolyte containing water. The secondary battery of the present invention is preferably a non-aqueous electrolyte secondary battery using a “non-aqueous” electrolyte as the electrolyte. The electrolyte may have a form such as liquid or gel (in the present specification, “liquid” non-aqueous electrolyte is also referred to as “non-aqueous electrolyte solution”).

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). In one preferred embodiment of the present invention, a combination of cyclic carbonates and chain carbonates is used as the non-aqueous electrolyte, for example, a mixture of ethylene carbonate and diethyl carbonate. Further, as a specific nonaqueous electrolyte solute, for example, a Li salt such as LiPF ₆ or LiBF ₄ is preferably used. Further, as a specific nonaqueous electrolyte solute, for example, a Li salt such as LiPF ₆ or LiBF ₄ is preferably used.

  The exterior body is usually a conductive hard case, and includes a main body portion and a lid portion. A main-body part consists of the bottom part and side part which comprise the bottom face of the said exterior body. The main body and the lid are sealed after the electrode assembly, the electrolyte, the current collecting lead, and the external terminal are accommodated. The sealing method is not particularly limited, and examples thereof include a laser irradiation method. As a material constituting the main body part and the lid part, any material capable of constituting a hard case type exterior body in the field of secondary batteries can be used. Such a material may be any material that can achieve electron transfer, and examples thereof include conductive materials such as aluminum, nickel, iron, copper, and stainless steel. The dimensions of the main body and the lid are mainly determined according to the dimensions of the electrode assembly. For example, when the electrode assembly is accommodated, the dimensions are such that the electrode assembly is prevented from moving (displacement) within the exterior body. It is preferable to have. By preventing the movement of the electrode assembly, the electrode assembly is prevented from being destroyed, and the safety of the secondary battery is improved. The exterior body may be a flexible case such as a pouch made of a laminate film as long as it has conductivity.

  As the spacer, any spacer used in the field of secondary batteries can be used. The material constituting the spacer is not particularly limited, and examples thereof include various insulating polymers such as polyolefin (polyethylene, polypyropylene), polyester (polyethylene terephthalate, polybutylene terephthalate), and acrylic polymer. The spacer is not particularly limited, but may have a film or non-woven fabric form.

  As the current collecting lead for the positive electrode and the current collecting lead for the negative electrode, any current collecting lead used in the field of secondary batteries can be used. Such a current collecting lead may be made of a material that can achieve electron movement, and is made of a conductive material such as aluminum, nickel, iron, copper, and stainless steel. The positive electrode current collector lead is preferably composed of aluminum, and the negative electrode current collector lead is preferably composed of nickel. The form of the positive electrode current collector lead and the negative electrode current collector lead is not particularly limited, and may be, for example, a wire or a plate.

[Characteristics of the secondary battery of the present invention]
The secondary battery 100 according to an embodiment of the present invention is characterized by its shape. FIG. 1 is a schematic plan view of a secondary battery according to an embodiment of the present invention. In the present invention, as shown in FIG. 1, a concave surface 11 that is recessed toward the inside is formed on a part of the contour surface 10 of the secondary battery 100. The concave surface 11 includes a curved surface 12 at least at a part thereof. As shown in FIG. 1, the curved surface 12 is an inner curved surface that is curved toward the inner side. In particular, in the present invention, the bending angle θ of the curved surface 12 is 90 ° or more and 180 ° or less with the bending center point C as a base point. Here, the “curvature center point” refers to a point equidistant from one end of the curved surface, the other end of the curved surface, and an intermediate point between one end and the other end of the curved surface. Specifically, as shown in FIG. 7, the “curvature center point” means a distance R with one end of the curved surface, a distance R ′ with the intermediate point of the curved surface, and a distance R with the other end of the curved surface. '' Refers to the point where both are equal. In the secondary battery according to the embodiment of the present invention, as described above, the type of the electrode assembly is roughly divided into two types, that is, a planar stacked structure type and a wound structure type, and therefore the shape of the electrode assembly is different. Although obtained, the shape of the exterior body does not change in a plan view or a side view. Therefore, it is preferable that the exterior body, which is a constituent element of the secondary battery according to the embodiment of the present invention, has a curved surface that is curved at least inward in a plan view or a side view. In addition, it is preferable that the electrode assembly of the planar laminated structure type also has a curved surface that is curved inwardly in a plan view or a side view. However, the present invention is not limited to this, and the wound structure type electrode assembly may also have a curved surface curved inward in a plan view or a side view.

  In the present invention, since the curved surface 12 curved inwardly is formed on a part of the contour surface 10 of the secondary battery 100, the shape of the electronic medium connected to the secondary battery 100 depends on the application. Therefore, the shape of the curved surface 12 of the secondary battery 100 and the shape of the electronic medium have the same or similar shape. For this reason, it becomes easy to fit the curved electronic medium into the region where the curved surface of the secondary battery is formed. That is, the curved surface 12 formed in the secondary battery 100 functions as a surface for arranging an electronic medium having a curved shape. Thereby, even when the shape of the electronic medium is a curved shape, the electronic medium can be efficiently installed on the secondary battery in the electronic device. Therefore, it is possible to meet demands for thinning and miniaturization of electronic devices.

  In one embodiment, all of the concave surface 11 formed in the inner direction on a part of the contour surface 10 of the secondary battery 100 may be the curved surface 12 according to the curved shape / size of the electronic medium. In this case, the curvature center point C is located outside the extending shaft 14 of the non-concave surface 13 that is continuous with the concave surface 11 (see FIGS. 2 and 3). As an example in which the bending center point C is outside the extending axis 14, for example, as shown in FIG. 2, there is a case where the bending angle of the curved surface 12 formed in the secondary battery 100 is 90 °. Further, as an example in which the bending center point C is outside the extending axis 14, for example, as shown in FIG. 3, the bending angle of the bending surface 12 formed in the secondary battery 100 is 120 °. It is done. Further, the center C of curvature may be on the extending axis 14 of the non-concave surface 13 that is continuous with the concave surface 11 (see FIG. 4). As an example in which the bending center point C is on the extending axis 14, for example, as shown in FIG. 4, there is a case where the bending angle of the bending surface 12 formed in the secondary battery 100 is 180 °.

  In another aspect, only a part of the concave surface 11 formed in the inner direction on a part of the contour surface 10 of the secondary battery 100 is the curved surface 12 according to the curved shape and size of the electronic medium. It's okay. Specifically, as shown in FIG. 5, a curved surface 12 having a curved angle of 180 ° may be formed at a substantially intermediate position of the concave surface 11. In this case, of the concave surface 11, the surface excluding the curved surface 12 has a substantially planar shape, and the curved center point C is located on the inner side of the extending axis 14 of the non-concave surface 13 that is continuous with the concave surface 11. become. When a part of the concave surface 11 is a curved surface 12, an electronic medium having a shape having both a substantially flat portion and a curved portion is fitted in the region where the concave surface 11 of the secondary battery 100 is formed. It becomes possible.

  In another aspect, as shown in FIG. 6, the two secondary batteries 100 may be arrange | positioned so that the curved surfaces 12 may mutually oppose. In this aspect, in order to arrange the two secondary batteries 100 so as to be in contact with each other while the curved surfaces 12 are opposed to each other, the curved angle of the curved surface 12 is 160 ° or more in any secondary battery 100. It is preferable that it is 180 degrees or less. When the two secondary batteries are arranged so that the curved surfaces 12 face each other, a substantially circular region is formed in a plan view or a side view as shown in FIG. This makes it possible to arrange the curved electronic medium so as to be accommodated in the substantially circular region. Therefore, even when the shape of the electronic medium is a curved shape, the electronic medium can be more efficiently installed with respect to the secondary battery in the electronic device.

  In still another aspect, when all the concave surfaces are curved surfaces (see FIGS. 2 to 4), an R chamfered portion is formed on at least one of one end of the curved surface and the other end of the curved surface. Is preferred. When the R chamfered portion is formed, the contact resistance between the electronic medium and the curved surface can be reduced when an electronic medium having a curved shape is provided in the region where the curved surface of the secondary battery is formed. it can. Therefore, the electronic medium having a curved shape can be smoothly fitted in the region where the curved surface of the secondary battery is formed. Similarly, when only a part of the concave surface is a curved surface (see FIG. 5), it is preferable that an R chamfered portion is formed on at least one of the one end of the concave surface and the other end of the concave surface. When the R chamfered portion is formed, the contact resistance between the electronic medium and the concave surface can be reduced when the curved electronic medium is provided in the region where the concave surface of the secondary battery is formed. Therefore, the electronic medium having a curved shape can be smoothly fitted in the region where the concave surface of the secondary battery is formed.

  If the bending angle θ of the curved surface is 180 ° or less with the bending center point C as a base point, when the conductive hard case (metal can) is used as the exterior body as described above, the laser is uniformly irradiated to the welded portion. There is also an effect that it is possible. Further, when the bending angle θ of the curved surface is 180 ° or less with the bending center point C as a base point, when using a flexible case such as a pouch made of a laminate film as the exterior body as described above, it is easy to weld using a laser. The effect is also produced.

  The secondary battery according to an embodiment of the present invention can be used in various fields where power storage is assumed. The secondary battery according to an embodiment of the present invention, particularly the non-aqueous electrolyte secondary battery, is merely an example, and the electric / information / communication field (for example, a mobile phone, a smart phone, a notebook) Mobile devices such as personal computers and digital cameras), home / small industrial applications (eg, power tools, golf carts, home / care / industrial robots), large industrial applications (eg, forklifts, elevators, bay ports) Crane field), transportation system field (for example, hybrid vehicle, electric vehicle, bus, train, electric assist bicycle, electric motorcycle, etc.), power system application (for example, various power generation, road conditioner, smart grid, general home installation) Field), as well as space and deep sea applications (eg space probes) It can be used in the field), such as diving research vessel.

100 Secondary Battery 10 Contour Surface 11 Concave Surface 12 Curved Surface 13 Non-Curved Surface 14 Axis of Extension of Non-Curved Surface C Curvature Center Point θ Curvature Angle

Claims (8)

An electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and an electrolyte, and a secondary battery in which an electrolyte is housed,
A concave surface that is recessed inwardly is formed in a part of the contour surface of the secondary battery, and a curved surface is formed in at least a part of the concave surface, and a curved angle of the curved surface is a center point of curvature The bending center point is from one of the one end of the curved surface, the other end of the curved surface, and the intermediate point between the one end and the other end of the curved surface. A secondary battery characterized in that it also points to an equidistant point.   When all of the concave surfaces are the curved surfaces, the central point of curvature is on an extension axis of a non-concave surface continuous with the concave surface or on an outer side of the extension axis. The secondary battery as described.   When the curved surface is formed in a part of the concave surface and the curved angle is 180 °, the curved center point is located on the inner side of the extending axis of the non-concave surface that is continuous with the concave surface. The secondary battery according to claim 1.   The secondary battery according to claim 1, wherein the exterior body has at least the curved surface.   The secondary battery according to claim 1, wherein the curved surface is a surface on which an electronic medium having a curved shape is arranged.   The secondary battery according to claim 1, wherein an R chamfered portion is formed on at least one of the one end of the concave surface and the other end of the concave surface.   The secondary battery according to claim 1, wherein the positive electrode and the negative electrode are electrodes capable of occluding and releasing lithium ions. The positive electrode includes 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 as a positive electrode active material,
The secondary battery according to claim 1, wherein the negative electrode contains a carbon material as a negative electrode active material.

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