WO2017209052A1

WO2017209052A1 - Secondary battery

Info

Publication number: WO2017209052A1
Application number: PCT/JP2017/019918
Authority: WO
Inventors: 昌史樋口
Original assignee: 株式会社村田製作所
Priority date: 2016-05-31
Filing date: 2017-05-29
Publication date: 2017-12-07

Abstract

The present invention provides a secondary battery which is sufficiently reduced in the impedance, while achieving a reduced thickness (smaller size) and a higher capacity. The present invention relates to a secondary battery 100A wherein an electrode assembly and an electrolyte are sealed in an outer case 6, said electrode assembly comprising a positive electrode, a negative electrode and a separator that is arranged between the positive electrode and the negative electrode. The secondary battery 100A has a shape that is provided with an incision 8 when viewed in plan, and comprises sealing parts 91a, 91b in a peripheral part of the secondary battery, said peripheral part being adjacent to the incision 8, while having two external terminals 5 that protrude from the sealing parts toward the incision 8. This secondary battery 100A is arranged such that at least a part of the sealing parts 91a, 91b overlaps an end of a circuit board.

Description

Secondary battery

The present invention relates to a secondary battery.

Conventionally, secondary batteries have been used as power sources for various electronic devices. A secondary battery generally has a structure in which an electrode assembly (electrode body) and an electrolyte are accommodated in an exterior body (case), and further includes an external terminal for achieving electrical connection of the secondary battery. ing.

In recent years, electronic devices are becoming thinner and smaller, and accordingly, demands for thinner and smaller secondary batteries are increasing. Also, most lithium ion secondary batteries require a protective circuit board for the purpose of preventing overcharge, overdischarge, overcurrent, and the like.

For this reason, a technique has been reported in which a notch is provided in a secondary battery and a protective circuit board is disposed there (Patent Document 1). Specifically, as shown in FIG. 9A, for example, the secondary battery 500 has a shape including a notch 508, and seals 509a to 509f for holding an electrolyte or the like in the exterior body 506 at the periphery thereof. have. Of these seal portions, two external terminals 505 projecting toward the notch portion 508 are arranged in the

seal portions

509 a and 509 b adjacent to the notch portion 508. Further, the surface of the secondary battery 500 is formed of an exterior body 506. In general, in such a secondary battery 500, as shown in FIG. 9B, the protection circuit board 600 has a peripheral portion (seal portion) of the secondary battery 500 from the viewpoint of reducing the influence of heat generated by the secondary battery 500. 509a, 509b) through a predetermined gap x, and arranged in the notch 508. The seal portion is formed by heat sealing when the outer package 506 is a flexible pouch made of, for example, a laminate film.

JP 2016-506606 A

However, the inventors of the present invention have found that such a secondary battery 500 causes the following new problem.
(1) By securing the gap x, the external terminal 505 becomes longer by that amount, and the impedance of the secondary battery increases. Therefore, the effect of heat generation of the secondary battery cannot be reduced sufficiently.
(2) Since the gap x is a dead space for the secondary battery, it is disadvantageous for making the secondary battery thinner, smaller, and higher capacity.
(3) The electrolyte leaked from the seal portion 509b from which the external terminal 505 protruded. For this reason, when the width y1 of the seal portion 509b is made wider than the width of other seal portions (for example, the width y2 of the seal portion 509a), the problems (1) and (2) are remarkable.

An object of the present invention is to provide a secondary battery in which the impedance of the secondary battery is sufficiently reduced, and a reduction in thickness (miniaturization) and an increase in capacity are achieved.

The present invention provides a secondary battery in which the impedance of the secondary battery is sufficiently reduced even when the width of the seal portion from which the external terminal protrudes is widened, and the thickness is reduced (downsized) and the capacity is increased. For the purpose.

The present invention is a secondary battery in which 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 are enclosed in an outer package,
The secondary battery has a shape with a notch portion in plan view, and has a seal portion at the peripheral edge of the secondary battery adjacent to the notch portion, and the seal portion to the notch portion. Two external terminals protruding toward the
The secondary battery relates to a secondary battery that is arranged so that at least a part of the seal portion overlaps an end portion of a circuit board.

The secondary battery of the present invention is arranged so that the seal portion overlaps the circuit board without securing the gap x between the circuit board and the prior art. Thereby, since an external terminal can be shortened, the impedance of a secondary battery can be reduced and heat generation can be sufficiently prevented. Further, since the formation of a dead space for the secondary battery is avoided, the secondary battery can be made thinner and smaller, and the battery capacity can be increased.
Such an effect of the present invention can be effectively obtained even when the width of the seal portion from which the external terminal protrudes is widened to prevent electrolyte leakage.

The schematic plan view when the secondary battery which concerns on the 1st embodiment of this invention is seen from the thickness direction is shown. 1B is a schematic plan view showing the arrangement of the secondary battery and the circuit board in FIG. 1A. FIG. The schematic plan view when another example of the secondary battery which concerns on the 1st embodiment of this invention is seen from the thickness direction is shown. The schematic plan view showing arrangement | positioning with the secondary battery of FIG. 2A and a circuit board is shown. The schematic plan view when another example of the secondary battery which concerns on the 1st embodiment of this invention is seen from the thickness direction is shown. The schematic plan view showing arrangement | positioning with the secondary battery of FIG. 3A and a circuit board is shown. The schematic plan view when the secondary battery which concerns on the 2nd embodiment of this invention is seen from the thickness direction is shown. The schematic plan view showing arrangement | positioning with the secondary battery of FIG. 4A and a circuit board is shown. The schematic plan view when the secondary battery which concerns on the 3rd embodiment of this invention is seen from the thickness direction is shown. The schematic plan view showing arrangement | positioning with the secondary battery of FIG. 5A and a circuit board is shown. The schematic plan view when the secondary battery which concerns on the 4th embodiment of this invention is seen from the thickness direction is shown. FIG. 6B is a schematic plan view showing the arrangement of the secondary battery and the circuit board in FIG. 6A. The schematic plan view when the secondary battery which concerns on the 5th embodiment of this invention is seen from the thickness direction is shown. The schematic plan view showing arrangement | positioning with the secondary battery of FIG. 7A and a circuit board is shown. FIGS. 1B, 2B, 3B, 4B, 5B, 6B, and 7B show examples of schematic enlarged cross-sectional views as seen in the direction of the arrows. FIGS. 1B, 2B, 3B, 4B, 5B, 6B, and 7B show examples of schematic enlarged cross-sectional views as seen in the direction of the arrows. FIGS. 1B, 2B, 3B, 4B, 5B, 6B, and 7B show examples of schematic enlarged cross-sectional views as seen in the direction of the arrows. The schematic plan view when the secondary battery which concerns on a prior art is seen from the thickness direction is shown. FIG. 9B is a schematic plan view showing the arrangement of the secondary battery and the circuit board in FIG. 9A.

[Secondary battery and its arrangement]
The present invention provides a secondary battery. In this specification, the term “secondary battery” refers to a battery that can be repeatedly charged and discharged. The “secondary battery” is not excessively bound by the name, and may include, for example, “electric storage device”.

In the secondary battery of the present invention, an electrode assembly and an electrolyte, which will be described later, are enclosed in an exterior body, and in a plan view, a peripheral portion thereof has a seal portion (sealing for holding the electrolyte or the like inside the exterior body). Stop) is formed. The plan view is a state when the secondary battery is placed and viewed from directly above in the thickness (height) direction, and is in agreement with the plan view. The mounting is, for example, mounting with the surface of the maximum area of the secondary battery as the bottom surface.

Hereinafter, the secondary battery of the present invention will be described in detail with reference to the drawings, but various elements in the drawings are merely schematically and exemplarily shown for understanding of the present invention, and the appearance and size ratio, etc. Can be different from the real thing. The “vertical direction”, “left / right direction”, and “front / back direction” used directly or indirectly in this specification correspond to directions corresponding to the vertical direction, left / right direction, and front / back direction in the drawing, respectively. Unless otherwise specified, the same symbols or symbols indicate the same members or the same meaning.

The secondary battery of the present invention has a notch portion in plan view as shown in FIGS. 1A, 2A, 3A, 4A, 5A, 6A and 7A (hereinafter referred to as FIGS. 1A to 7A). 8, and at least a peripheral portion of the secondary battery adjacent to the notch 8 has a seal portion. The notch is a part where a part of the cutout is intentionally lost from the initial shape. The initial shape of the secondary battery before the formation of the notch is usually a quadrangular shape (for example, a rectangular shape). The rectangular shape includes so-called rectangles and squares, and is preferably rectangular. The secondary battery before the formation of the notch is a secondary battery when it is assumed that there is no notch. The seal part which a secondary battery has in the peripheral part adjacent to notch part 8 is a seal part adjacent to notch part 8 among the seal parts of the peripheral part which a secondary battery has in plane view, Hereinafter, it is also referred to as “adjacent seal portion”. Examples of such adjacent seal portions include

seal portions

91a and 91b in FIG. 1A,

seal portions

92a and 92b in FIG. 2A,

seal portions

93a and 93b in FIG. 3A, seal portion 94a in FIG. 4A, and seal portion 95a in FIG. 6A, and seal portions 97a in FIG. 7A. Hereinafter, the adjacent seal portions may be collectively indicated as “90”. 1A to 7A are schematic plan views of an example of a secondary battery according to the present invention as seen from its thickness direction.

The seal portion is provided at the peripheral portion of the exterior body so as to seal the electrode assembly, electrolyte, and the like inside the exterior body from the outside. The seal portion is formed by joining the overlapping portions of the exterior body. As long as an electrolyte or the like is held inside the exterior body, the seal portion does not necessarily have to be formed on all peripheral portions of the exterior body (secondary battery). For example, when the exterior body is formed from a laminate film and the laminate film is continuously used by being folded at the peripheral portion, the seal portion may not be formed at the peripheral portion.

The boundary 7 between the peripheral edge adjacent to the notch 8 and the notch 8 in the secondary battery may be defined by one or more straight lines, one or more curves, or a combination thereof. For example, the boundary 7 is defined by two straight lines in FIGS. 1A, 2A and 3A. For example, in FIG. 4A, the boundary 7 is defined by one straight line. Further, for example, in FIG. 5A, the boundary 7 is defined by one straight line and one curved line. For example, in FIG. 6A, the boundary 7 is defined by three straight lines. Further, for example, in FIG. 7A, the boundary 7 is defined by one curve. The curve includes an arc-shaped curve, a parabolic curve, and a curve in which a plurality of these curves are continuously connected.

The arrangement of the notches 8 included in the secondary battery may be appropriately selected according to the desired arrangement of the circuit board, and is not particularly limited. The notch 8 may be arranged, for example, so as to share one or two sides with the secondary battery before the notch is formed, or so as not to share any one side. From the viewpoint of the balance between the downsizing of the module including the secondary battery and the circuit board and the increase in capacity of the secondary battery, the arrangement of the notch portion 8 is preferably the secondary battery before the notch portion 8 is formed. And one or two, especially two sides are shared.

The arrangement in which the notch 8 shares two sides with the secondary battery before the notch is formed is an arrangement in which the notch 8 has one corner shared with the secondary battery. It means that the notch 8 has a shape including a corner in the secondary battery and is in a corner arrangement. The shape of the cutout 8 is not particularly limited, but for example, a quadrangular shape (particularly rectangular shape) shown in FIGS. 1A, 2A and 3A, a triangular shape shown in FIG. 4A, and a substantially trapezoidal shape shown in FIG. 5A. Examples include shape. At this time, the overall shape of the adjacent seal portion is, for example, a substantially L shape (FIGS. 1A, 2A and 3A), a substantially I shape (FIG. 4A), or a substantially J shape (FIG. 5A) in plan view. It may be.

The arrangement in which the cutout portion 8 shares one side with the secondary battery before the cutout portion is formed is an arrangement in which the cutout portion 8 has only one side shared with the secondary battery. It means that the notch 8 has a shape that does not include a corner in the secondary battery and is in an end portion arrangement. The shape of the notch 8 is not particularly limited, and examples thereof include a quadrangular shape (particularly a rectangular shape) shown in FIG. 6A. At this time, the overall shape of the adjacent seal portion may be, for example, a substantially U shape (FIG. 6A) in plan view.

The arrangement in which the cutout portion 8 does not share any side with the secondary battery before the cutout portion is formed is an arrangement in which the cutout portion 8 does not have any side shared with the secondary battery. Yes, it means that the notch 8 has a shape including neither a corner nor a side in the secondary battery, and is in a central arrangement. The shape of the notch 8 is not particularly limited, and examples thereof include a circular shape and a quadrangular shape (particularly a rectangular shape) shown in FIG. 7A. At this time, the overall shape of the adjacent seal portion may be, for example, a substantially O shape (FIG. 7A) in plan view.

The external terminal 5 protrudes from the adjacent seal part toward the notch. The secondary battery of the present invention has an external terminal in the adjacent seal part and the circuit board is arranged in the notch part, whereby the external terminal can be shortened. For this reason, the impedance of the secondary battery can be reduced and heat generation can be sufficiently prevented. The external terminal 5 includes a positive external terminal and a negative external terminal.

The width of the seal portion is not particularly limited as long as the outer package 6 can hold the electrolyte and the like. Usually, the width w1 of the seal portion from which the external terminal 5 protrudes is 0. 0 mm with respect to the thickness D (mm) of the secondary battery. It is 8 × D or more and 3 × D or less, particularly 1 × D or more and 2 × D or less. The width w2 of the seal portion other than the seal portion from which the external terminal 5 protrudes is normally 0.5 × D or more and 2 × D or less, particularly 0.8 × D or more, relative to the thickness D (mm) of the secondary battery. 5 × D or less. From the viewpoint of preventing electrolyte leakage, w1 and width w2 preferably satisfy the relationship of w1 ≧ w2, particularly w1> w2, and more preferably satisfy the relationship of 2 × w2 ≧ w1> w2.

In particular, when the adjacent seal portion has an L shape (91a and 91b, 92a and 92b, and 93a and 93b) as shown in FIGS. 1A to 3A in plan view, the two external terminals 5 (the positive external terminal and the negative electrode) 1A to 2A, both of the external terminals may protrude from one straight portion (91b, 92a) of the L-shaped seal portion, or each L terminal as shown in FIG. 3A. You may protrude from one linear part (for example, 93a) and the other linear part (for example, 93b) of a character-shaped seal | sticker part. Even in such a case, it is preferable that the width w1 of the seal portion from which the external terminal 5 protrudes and the width w2 of the seal portion other than the seal portion from which the external terminal 5 protrudes are within the above ranges. Regarding the two straight portions constituting the L-shaped adjacent seal portion, the width of the straight portion from which the external terminal protrudes corresponds to the width w1, and the width of the straight portion from which the external terminal does not protrude corresponds to the width w2. It shall be. In FIGS. 1A to 3A, the widths of the

seal portions

91b, 92a, 93a, and 93b are preferably within the range of the width w1, and the widths of the other seal portions are preferably within the range of the width w2.

In the present invention, the secondary battery is arranged so that at least a part, preferably all, of the adjacent seal part overlaps the end part of the circuit board. The fact that at least a part of the adjacent seal part overlaps with the end part of the circuit board means that when the secondary battery and the circuit board arranged are seen through in a plan view, at least a part of the adjacent seal part of the secondary battery and the circuit board It means that it overlaps with the end. For example, in FIGS. 1B, 2B, 3B, 4B, 5B, 6B, and 7B (hereinafter referred to as FIGS. 1B to 7B), secondary batteries 100 (100A, 100B, 100C, 100D, 100E, 100F, 100G) part of the adjacent seal portion and the end of the circuit board 60 (60A, 60B, 60C, 60D, 60E, 60F, 60G) overlap. Thereby, since an external terminal can be shortened, the impedance of a secondary battery can be reduced and heat generation can be sufficiently prevented. Further, since the formation of a dead space for the secondary battery is avoided and the space can be used effectively, the secondary battery can be made thinner and smaller, and the battery capacity can be increased. 1B to 7B are schematic plan views showing the arrangement of the secondary battery and the circuit board in FIGS. 1A to 7A, respectively.

The ratio of the overlapping area by the circuit board in the adjacent seal portion is usually 50% or more, preferably 60% or more, more preferably 70% or more. The ratio of the overlapping area is a ratio with respect to the entire area of the adjacent seal portion. The area of the common part of the adjacent seal part and the seal part other than the adjacent seal part is included in the area of the adjacent seal part.

As shown in FIG. 8A, the adjacent seal portion 90 and the circuit board 60 of the secondary battery 100 are overlapped with each other by arranging the end portion of the circuit board 60 on the adjacent seal portion 90 from the viewpoint of simple overlapping arrangement. Is preferably achieved. The overlap may be achieved by placing the end of the circuit board 60 under the adjacent seal portion 90 as shown in FIG. 8B. As shown in FIG. 8C, the overlap may be achieved by the end portion of the circuit board 60 including the adjacent seal portion 90.

In particular, as shown in FIGS. 1A to 2A, the adjacent seal portion has an L shape (91a and 91b, 92a and 92b), and two external terminals 5 (a positive electrode external terminal and a negative electrode external terminal) When both project from the one straight portion (91b, 92a) of the L-shaped seal portion, the secondary battery (100A, 100B) has at least one straight portion (91b, 92a) of the L-shaped seal portion. May be arranged so as to overlap the end of the circuit board (60A, 60B). The ratio of the overlapping area due to the circuit board in the one straight line portion is not particularly limited as long as the ratio of the overlapping area due to the circuit board in the adjacent seal portion is within the above-described range, and is usually 60% or more, preferably 70. % Or more, more preferably 80% or more. The ratio of the overlapping area by the circuit board in the one straight part is a ratio to the total area of the one straight part constituting the adjacent seal part. The area of the common part of the one straight line portion (91b, 92a) and the other straight line portion (91a, 92b) is included in the area of the one straight line portion (91b, 92a).

In this case, from the viewpoint of further effective use of the space, the secondary battery (100A, 100B) has the one straight line portion (91b, 92a) of the L-shaped seal portion as shown in FIGS. 1B and 2B. In addition, the other straight portions (91a, 92b) are preferably arranged so as to overlap the end portions of the circuit boards (60A, 60B). The ratio of the overlapping area by the circuit board in the other straight part is usually 50% or more, preferably 60% or more, more preferably 70% or more. The ratio of the overlapping area is a ratio with respect to the total area of the other straight line portion constituting the adjacent seal portion.

In FIG. 1B and FIG. 2B, a part of the one straight part (91b, 92a) and a part of the other straight part (91a, 92b) of the L-shaped seal part are part of the circuit board (60A, 60B). Although overlapping with the end portion, from the viewpoint of further effective use of the space, all of the one straight portion (91b, 92a) and the other straight portion (91a, 92b) of the L-shaped seal portion Preferably overlaps the edge of the circuit board (60A, 60B).

The thickness D of the secondary battery is not particularly limited, and may be, for example, 1 mm or more and 100 mm or less. In particular, the thickness D of the secondary battery for mobile devices is preferably 5 mm or more and 50 mm or less.

[Components of secondary battery]
For example, as shown in FIGS. 8A, 8B, and 8C, the electrode assembly includes the positive electrode 1, the negative electrode 2, and the separator 3, and the positive electrode 1 and the negative electrode 2 are alternately arranged with the separator 3 interposed therebetween. The two external terminals 5 are connected to an electrode (positive electrode or negative electrode) via the current collecting lead 4 and, as a result, are led out from the seal portion. In these drawings, the electrode assembly has a planar laminated structure in which a plurality of electrode units (electrode constituent layers) including a positive electrode 1, a negative electrode 2, and a separator 3 arranged between the positive electrode 1 and the negative electrode 2 are laminated in a planar shape. have. The structure of the electrode assembly is not limited to a planar laminated structure. For example, an electrode unit (electrode constituent layer) including a positive electrode 1, a negative electrode 2, and a separator 3 disposed between the positive electrode 1 and the negative electrode 2 is wound in a roll shape. You may have the wound structure wound. The structure of the electrode assembly may be a so-called stack and folding method in which a positive electrode, a separator, and a negative electrode are stacked on a long film and then folded. 8A and 8B, the external terminal 5 is not connected to any member at the left end, but is usually electrically connected to a specific member. For example, the external terminal 5 may be electrically and directly connected to the circuit board 60, or may be electrically and indirectly connected to the circuit board 60 via another device.

The positive electrode 1 is composed of at least a positive electrode material layer and a positive electrode current collector (foil), and it is sufficient that the positive electrode material layer is provided on at least one surface of the positive electrode current collector. For example, in the positive electrode 1, a positive electrode material layer may be provided on both surfaces of the positive electrode current collector, or a positive electrode material layer may be provided on one surface of the positive electrode current collector. The positive electrode 1 preferable from the viewpoint of further increasing the capacity of the secondary battery is provided with a positive electrode material layer on both surfaces of the positive electrode current collector. The positive electrode material layer contains a positive electrode active material.

The negative electrode 2 is composed of at least a negative electrode material layer and a negative electrode current collector (foil), and it is sufficient that the negative electrode material layer is provided on at least one surface of the negative electrode current collector. For example, in the negative electrode 2, the negative electrode material layer may be provided on both surfaces of the negative electrode current collector, or the negative electrode material layer may be provided on one surface of the negative electrode current collector. From the viewpoint of further increasing the capacity of the secondary battery, the negative electrode 2 is preferably provided with a negative electrode material layer on both surfaces of the negative electrode current collector. The negative electrode material layer contains a negative 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. As will be described later, 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, it is also preferable that a conductive additive is 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 this embodiment, 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. In a more preferred embodiment, the positive electrode active material contained in the positive electrode material layer is lithium cobalt oxide.

The binder that can be included in the positive electrode material layer is not particularly limited, but includes 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. 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, 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. 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, 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. In a more preferred embodiment, the binder contained in the negative electrode material layer is styrene butadiene rubber. The conductive aid 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.

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 3 is a member provided from the viewpoints of preventing a 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 membrane used as the separator may include, for example, only polyethylene (PE) or only polypropylene (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 and / or an adhesive layer. The surface of the separator may have adhesiveness.

Electrolyte helps the movement of metal ions released from the electrodes (positive and negative electrodes). The electrolyte may be a “non-aqueous” electrolyte, such as an organic electrolyte and an organic solvent, or may be a “aqueous” electrolyte containing water. The secondary battery of the present invention is preferably a non-aqueous electrolyte secondary battery in which an electrolyte containing a “non-aqueous” solvent and a solute is used as an 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.
As specific nonaqueous electrolyte solutes, for example, Li salts such as LiPF ₆ and LiBF ₄ are preferably used.

As the current collecting lead 4, 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 capable of achieving electron movement, and is usually made of a conductive material such as aluminum, nickel, iron, copper, and stainless steel. The form of the current collecting lead 4 is not particularly limited, and may be, for example, a linear shape or a plate shape.

As the external terminal 5, any external terminal used in the field of secondary batteries can be used. Such an external terminal may be made of a material capable of achieving electron movement, and is usually made of a conductive material such as aluminum, nickel, iron, copper, and stainless steel. The positive electrode external terminal is preferably made of aluminum, and the negative electrode external terminal is preferably made of copper. The form of the external terminal 5 is not particularly limited, and is usually plate-shaped.

The outer package 6 is preferably a flexible pouch (soft bag), but may be a hard case (hard housing). When the exterior body 6 is a flexible pouch, the flexible pouch is usually formed from a laminate film, and the peripheral portion is heat-sealed to form a seal portion. As the laminate film, a film obtained by laminating a metal foil and a polymer film is generally used. Specifically, a film having a three-layer structure including an outer layer polymer film / metal foil / inner layer polymer film is exemplified. The outer layer polymer film is for preventing damage to the metal foil due to permeation and contact of moisture and the like, and polymers such as polyamide and polyester can be suitably used. The metal foil is for preventing the permeation of moisture and gas, and a foil of copper, aluminum, stainless steel or the like can be suitably used. The inner layer polymer film is for protecting the metal foil from the electrolyte accommodated therein, and for melting and sealing at the time of heat sealing, and polyolefin or acid-modified polyolefin can be suitably used. The thickness of the laminate film is not particularly limited, and is preferably 1 μm or more and 1 mm or less, for example.

When the exterior body 6 is a hard case, the hard case is usually formed from a metal plate, and a peripheral portion is irradiated with a laser to form a seal portion. As the metal plate, a metal material made of aluminum, nickel, iron, copper, stainless steel or the like is common. The thickness of a metal plate is not specifically limited, For example, 1 micrometer or more and 1 mm or less are preferable.

[Circuit board]
The circuit board 60 may be a so-called rigid board or a flexible board. A rigid substrate is preferred. This is because formation of a dead space tends to be a problem when a rigid substrate is used, but even when a rigid substrate is used in the present invention, such a problem can be sufficiently avoided. As the rigid substrate, any rigid substrate used in the field of circuit boards used with secondary batteries can be used, and examples thereof include a glass / epoxy resin substrate.

When the circuit board is a so-called protection circuit board for preventing overcharge, overdischarge and overcurrent of the secondary battery, a secondary battery pack is constituted by the protection circuit board and the secondary battery.

The secondary battery according to the present invention can be used in various fields where power storage is assumed. The secondary battery according to 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 smart watch, a laptop computer) in which a mobile device is used. And mobile devices such as digital cameras), home / small industrial applications (eg, power tools, golf carts, home / care / industrial robots), large industrial applications (eg, forklifts, elevators, bay harbor cranes) Field), transportation system field (for example, fields such as hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles), power system applications (for example, various power generation, road conditioners, smart grids, general home-installed types) Fields such as power storage systems), as well as space and deep sea applications (for example, space)査機, it can be used in the field), such as diving research vessel.

1: Positive electrode 2: Negative electrode 3: Separator 4: Current collecting lead 5: External terminal 6: Exterior body 7: Boundary between peripheral edge and notch 8: Notch 60: 60A to 60G: Circuit board 90: 91a to 91f: 92a to 92f: 93a to 93f: 94a to 94e: 95a to 95e: 96a to 96h: 97a to 97e: Seal part 100: 100A to 100G: Secondary battery

Claims

An electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and a secondary battery in which an electrolyte is enclosed in an exterior body,
The secondary battery has a shape with a notch portion in plan view, and has a seal portion at the peripheral edge of the secondary battery adjacent to the notch portion, and the seal portion to the notch portion. Two external terminals protruding toward the
The secondary battery is a secondary battery arranged such that at least a part of the seal portion overlaps an end portion of the circuit board.
The boundary between the peripheral edge of the secondary battery adjacent to the notch and the notch is defined by one or more straight lines, one or more curves, or a combination thereof. Next battery.
The secondary battery before forming the notch has a rectangular shape,
3. The secondary battery according to claim 1, wherein the notch is disposed so as to share two sides with the secondary battery before the notch is formed. 4.
The seal portion has an L shape in the plan view,
Both of the two external terminals protrude from one straight portion of the L-shaped seal portion,
The secondary battery according to any one of claims 1 to 3, wherein the secondary battery is disposed so that at least one of the straight portions of the L-shaped seal portion overlaps an end portion of the circuit board.
The secondary battery according to claim 4, wherein the secondary battery is arranged so that the other straight portion of the L-shaped seal portion also overlaps an end portion of the circuit board.
The secondary battery according to any one of claims 1 to 5, wherein a width w1 of the seal portion from which the external terminal protrudes and a width w2 of a seal portion other than the seal portion from which the external terminal protrudes satisfy the following relational expression:
w1 ≧ w2
The secondary battery according to any one of claims 1 to 6, wherein the exterior body is a flexible pouch or a hard case.
The electrode assembly has a planar stacked structure in which a plurality of electrode units including the positive electrode, the negative electrode, and the separator are stacked in a planar shape, or the electrode unit including the positive electrode, the negative electrode, and the separator is rolled. The secondary battery according to any one of claims 1 to 7, which has a wound structure.
The secondary battery according to any one of claims 1 to 8, wherein the circuit board is a rigid board or a flexible board.
The secondary battery according to any one of claims 1 to 9, wherein the circuit board is a protective circuit board.
The secondary battery according to any one of claims 1 to 10, wherein the positive electrode and the negative electrode have a layer capable of inserting and extracting lithium ions.
A device comprising: the secondary battery according to claim 1; and a circuit board disposed so as to overlap at least an end portion with the seal portion.
The circuit board is a protective circuit board;
The device according to claim 12, wherein the device is a secondary battery pack.
The device according to claim 12 or 13, wherein the device is a mobile device.