JPWO2020071362A1 - Secondary battery - Google Patents

Abstract

An electrode assembly having a positive electrode tab connection portion in which tabs provided for a plurality of positive electrodes are connected to each other and a negative electrode tab connection portion in which tabs provided for a plurality of negative electrodes are connected to each other. A secondary battery is provided. In the secondary battery of the present invention, when four battery compartments divided by the first virtual equalization bisection line and the second virtual equalization dichotomy line are virtualized in the plan view, positive electrode tabs are connected to the same compartment and adjacent compartments. The tab connection portion is arranged so that both the portion and the negative electrode tab connection portion do not exist.

Description

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

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

In such various applications, the secondary battery is often used for a relatively long period of time, and the secondary battery is often exposed to harsh conditions.

Japanese Unexamined Patent Publication No. 2018-14194

The inventor of the present application noticed that there are still problems to be overcome with the conventional secondary battery, and found that it is necessary to take measures for that purpose. Specifically, the inventor of the present application has found that there are the following problems.

The secondary battery has an electrode assembly in which an electrode constituent layer including a separator is laminated between the positive electrode and the negative electrode, and when an impact is applied to the secondary battery and the electrode assembly is divided, the electrode assembly is divided. Internal short circuit may occur due to division.

The safety of the secondary battery from the viewpoint of such division can be evaluated by a "crash test", but the inventor of the present application finds that the secondary battery is particularly prone to heat generation and / or ignition due to an internal short circuit during division. I found that it could be.

Specifically, it was found that when the electrode assembly is divided by an impact or the like, an excessively high temperature is brought about in the internal short-circuited portion generated by the division, and the secondary battery may generate heat and / or ignite. rice field. This is because all the layers of the positive electrode and the negative electrode of the electrode assembly are connected so as to contribute to the battery reaction, and due to such connection, a large current flows through the internal short circuit portion and a large amount of Joule heat is generated. (See FIG. 15).

It can be said that the secondary battery, which can be a problem in the collision test, is a battery in which heat generation and / or ignition is likely to occur due to the same internal short circuit even in an actual usage environment, and there is a concern in terms of safety.

The present invention has been made in view of such a problem. That is, a main object of the present invention is to provide a secondary battery which is less likely to cause excessive heat generation and / or ignition at the time of division and therefore has improved safety in an actual use environment.

The inventor of the present application has attempted to solve the above problems by dealing with it in a new direction, rather than dealing with it as an extension of the prior art. As a result, the invention of the secondary battery which achieved the above-mentioned main purpose was reached.

The present invention is a secondary battery comprising an electrode assembly comprising a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode.
It has a positive electrode tab connection portion in which tabs provided for a plurality of positive electrodes are connected to each other, and a negative electrode tab connection portion in which tabs provided for a plurality of negative electrodes are connected to each other.
In the plan view of the secondary battery, if four battery compartments divided by the first virtual equalization bisection line and the second virtual equalization dichotomy line orthogonal to each other are virtualized, the positive electrode tab connection portion is connected to the same compartment and the adjacent compartment. The arrangement of the tab connection part is such that both the negative electrode tab connection part and the negative electrode tab connection part do not exist.
A secondary battery is provided in which at least one of the positive electrode tab connection portion and the negative electrode tab connection portion does not have a lead and is not provided to an external terminal of the secondary battery.

The secondary battery of the present invention is less likely to cause excessive heat generation and / or ignition when it is divided, and therefore has improved safety in an actual use environment.

Specifically, in the secondary battery of the present invention, for each of the four virtual plane compartments, the tab connection portion is arranged so that neither the positive electrode tab connection portion nor the negative electrode tab connection portion exists in the same compartment and the adjacent compartment. Therefore, even if the electrode assembly is divided by a collision test or the like, an inconvenient short circuit that generates a large amount of Joule heat is unlikely to occur. In particular, even if the electrode assembly is divided or broken as represented by a collision test, all layers of the divided body or the broken body are not electrically connected, and an internal short circuit occurs in a part of the divided body or the broken body. However, it is difficult for all layers to be short-circuited. Therefore, in the secondary battery of the present invention, an inconvenient phenomenon such that a large current flows through the short-circuited portion and a large amount of Joule heat is generated is unlikely to occur.

Cross-sectional view schematically showing the electrode constituent layers Schematic plan view of an electrode assembly to illustrate the four virtual battery compartments Schematic plan view and cross-sectional view of an electrode assembly showing an arrangement relationship between a positive electrode tab connection portion and a negative electrode tab connection portion according to an embodiment of the present invention. Schematic plan view of the electrode assembly for explaining the first virtual equal bisected line and the second virtual equal bisected line. Schematic diagram for explaining a collision test A plan view and a cross-sectional view schematically showing an electrode assembly according to an embodiment of the present invention. Schematic plan view and cross-sectional view of an electrode assembly showing a reference example compared with the present invention. Schematic plan view of an electrode assembly showing a reference example compared with the present invention A plan view and a cross-sectional view schematically showing an electrode assembly according to the first aspect of the present invention. A plan view and a cross-sectional view schematically showing an electrode assembly according to the second aspect of the present invention. A plan view and a cross-sectional view schematically showing an electrode assembly according to the third aspect of the present invention. A plan view and a cross-sectional view schematically showing an electrode assembly according to a fourth aspect of the present invention. Schematic diagram for explaining "non-rectangular shape" ("partially notched shape") Schematic diagram for explaining the phenomenon that the inflow of a large current is prevented Schematic diagram for explaining the phenomenon in which a large current flows into a short-circuited portion due to division, resulting in excessive heat generation and ignition (conventional example).

Hereinafter, the secondary battery according to the embodiment of the present invention will be described in more detail. Although explanations will be given with reference to the drawings as necessary, the various elements in the drawings are merely schematically and exemplified for the understanding of the present invention, and the appearance, dimensional ratio, etc. may differ from the actual ones. ..

The "thickness" direction, which is directly or indirectly described herein, is based on the stacking direction of the electrode materials that make up the secondary battery. For example, in the case of a "secondary battery having a plate-like thickness" such as a flat battery, the direction of "thickness" corresponds to the plate thickness direction of such a secondary battery. In the present specification, the "cross-sectional view" is based on a virtual cross-section of an object obtained by cutting along the thickness direction of the secondary battery. Further, the "plan view" used in the present specification is based on a sketch when the object is viewed from above or below along the direction of such thickness.

Further, the "vertical direction" and the "horizontal direction" used directly or indirectly in the present specification correspond to the vertical direction and the horizontal direction in the drawings, respectively. Unless otherwise specified, the same code or symbol shall indicate the same member or the same meaning. In one preferred embodiment, it can be considered that the vertical downward direction (that is, the direction in which gravity acts) corresponds to the "downward direction" and the opposite direction corresponds to the "upward direction".

[Basic configuration of secondary battery]
The term "secondary battery" as used herein refers to a battery that can be repeatedly charged and discharged. Therefore, the secondary battery according to the present invention is not overly bound by its name, and may include, for example, a power storage device.

The secondary battery according to the present invention includes an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are laminated. FIG. 1 illustrates the electrode assembly 100. As shown in the drawing, the positive electrode 3 and the negative electrode 4 are stacked with each other via the separator 5 to form an electrode constituent layer 8, and at least one or more of the electrode constituent layers 8 are laminated to form an electrode assembly. There is. In a secondary battery, such an electrode assembly is enclosed in an exterior body together with an electrolyte (for example, a non-aqueous electrolyte).

The positive electrode is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, a positive electrode material layer is provided on at least one 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 be provided with positive electrode material layers on both sides of the positive electrode current collector, or may be provided with positive electrode material layers on only one side of the positive electrode current collector. .. From the viewpoint of further increasing the capacity of the secondary battery, it is preferable that the positive electrode is provided with positive electrode material layers on both sides 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, each of the plurality of negative electrodes in the electrode assembly may be provided with a negative electrode material layer on both sides of the negative electrode current collector, or may be provided with a negative electrode material layer on only one side of the negative electrode current collector. .. From the viewpoint of further increasing the capacity of the secondary battery, it is preferable that the negative electrode is provided with negative electrode material layers 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 substances that are directly involved in the transfer of electrons in the secondary battery, and are the main substances of the positive and negative electrodes that are responsible for charge / discharge, that is, the battery reaction. be. More specifically, ions are brought to the electrolyte due to the "positive electrode active material contained in the positive electrode material layer" and the "negative electrode active material contained in the negative electrode material layer", and such ions are transferred between the positive electrode and the negative electrode. The electrons are transferred and charged / 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, it is preferable that the non-aqueous electrolyte secondary battery is a non-aqueous electrolyte secondary battery in which lithium ions move between the positive electrode and the negative electrode via the non-aqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charging / 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 discharging lithium ions.

When the positive electrode active material of the positive electrode material layer is composed of particles, for example, a binder may be contained in the positive electrode material layer for more sufficient contact between particles and shape retention. Further, a conductive auxiliary agent may be contained in the positive electrode material layer in order to facilitate the transfer of electrons that promote the battery reaction. Similarly, when the negative electrode active material of the negative electrode material layer is composed of, for example, granules, it is preferable that the negative electrode active material contains a binder for more sufficient contact between the particles and shape retention, and facilitates the transfer of electrons that promote the battery reaction. A conductive auxiliary agent may be contained in the negative electrode material layer. As described above, since the form is composed of a plurality of components, the positive electrode material layer and the negative electrode material layer can also be referred to as a positive electrode mixture layer and a negative electrode mixture layer, respectively.

The positive electrode active material is preferably a substance that contributes to the occlusion and release of lithium ions. From this point of view, the positive electrode active material may be, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material may be 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 contained as the positive electrode active material. For example, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium iron phosphate, or a part of the transition metal thereof replaced with another metal. Such a positive electrode active material may be contained as a single species, but may be contained in combination of two or more species.

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

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

Various carbon materials for the negative electrode active material include graphite (natural graphite, artificial graphite), MCMB (mesocarbon microbeads), graphitized carbon, easily graphitized carbon, surface decorative graphite, hard carbon, soft carbon, and / Alternatively, diamond-like carbon and the like can be mentioned. In particular, graphite is preferable because it has high electron conductivity and excellent adhesion to a 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. It is preferable that such an oxide is amorphous as its structural form. This is because deterioration due to non-uniformity such as grain boundaries or defects is less likely to occur.

The binder that can be contained 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-based resin, and polyamide-imide-based 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 contained in the negative electrode material layer is not particularly limited, but is limited to carbon black such as thermal black, furnace black, channel black, ketjen black and acetylene black, graphite, carbon nanotubes, and vapor phase growth. At least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel and silver, and polyphenylene derivatives can be mentioned. The negative electrode material layer may contain a component derived from a thickener component (for example, carboxylmethyl cellulose) used at the time of manufacturing the battery.

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 by the active material due to the battery reaction. Such a current collector may be a sheet-shaped metal member and may have a perforated or perforated form. For example, the current collector may be a metal leaf, a punching metal, a net, an expanded metal, or the like. The positive electrode current collector used for the positive electrode is preferably made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel and the like, and may be, for example, an aluminum foil. On the other hand, the negative electrode current collector used for the negative electrode is preferably one 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 viewpoint of preventing a short circuit due to contact between the positive and negative electrodes and retaining an electrolyte. In other words, the separator can be said to be a member through which ions 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 morphology due to its small thickness. Although only an example, a microporous polyolefin membrane may be used as the separator. In this regard, the microporous membrane used as the separator may contain, for example, only polyethylene (PE) or 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 or the like. The surface of the separator may have adhesiveness. In the present invention, the separator should not be particularly bound by its name, and may be a solid electrolyte, a gel-like electrolyte, and / or an insulating inorganic particle having the same function.

In the secondary battery according to the present invention, an electrode assembly composed of an electrode constituent layer including a positive electrode, a negative electrode and a separator is enclosed in an outer body 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 an "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 emitted from the electrodes (positive electrode / negative electrode) are present, 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. The specific solvent for the non-aqueous electrolyte may contain at least carbonate. Such carbonates may be cyclic carbonates and / or chain carbonates. Although not particularly limited, 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 only an example, a combination of cyclic carbonates and chain carbonates may be used as the non-aqueous electrolyte, and for example, a mixture of ethylene carbonate and diethyl carbonate may be used. Further, as a specific non-aqueous electrolyte solute, for example, a Li salt such as _{LiPF 6} and / or LiBF _{4 is preferably used.} The non-aqueous electrolyte may be made of a chemical gel.

The exterior body 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 the form of a hard case or even in the form of a soft case. 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 laminated film.

[Characteristics of the secondary battery of the present invention]
The secondary battery of the present invention is characterized by the structure of its electrode assembly. In particular, it is characterized by the arrangement of the tab connection portions of the positive electrode and the negative electrode in the plan view of the electrode assembly. That is, in the secondary battery of the present invention, a positive electrode tab connection portion in which tabs provided for a plurality of positive electrodes are connected to each other and a negative electrode tab connection in which tabs provided for a plurality of negative electrodes are connected to each other are connected. It is characterized by the arrangement of the parts.

Specifically, in the plan view of the secondary battery, if four battery compartments divided by the first virtual equalization bisection line and the second virtual equalization dichotomy line orthogonal to each other are virtualized, a positive electrode tab is placed in the same compartment. There is no such thing as both the connection part and the negative electrode tab connection part, and the positive electrode is straddling the compartments adjacent to each other (in short, straddling the compartments having a horizontal relationship). The tab connection portion is arranged so that the tab connection portion and the negative electrode tab connection portion do not exist separately.

In other words, the positive electrode tab connection is arranged in one of the four battery compartments, while the negative electrode tab connection is arranged in another compartment, and the positive tab connection is arranged. The section is not adjacent to each other and the section in which the negative electrode tab connection portion is arranged, that is, such a section does not have a horizontal relationship with each other in a plan view. That is, it can be said that the section in which the positive electrode tab connection portion is arranged and the section in which the negative electrode tab connection portion is arranged typically face each other in a diagonal direction in the plan view of the secondary battery. ..

This will be described with reference to FIG. FIG. 2 shows a plan view of a square or rectangular rectangular electrode assembly 100. In the present invention, four battery compartments (100A, 100B, 100C and 100D) divided by the first virtual equalization bisection line 1 and the second virtual equalization bidivision line 2 are assumed in the plan view of the electrode assembly 100. .. With respect to these four virtual compartments, the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 have an arrangement relationship shown in FIGS. 3 (A) to 3 (D).

As shown in FIG. 3A, when the positive electrode tab connection portion 10 is arranged in the first battery compartment 100A, the negative electrode tab connection portion 20 is in the third battery compartment 100C diagonally opposed to the first battery compartment. Have been placed. Similarly, as shown in FIG. 3B, when the positive electrode tab connection portion 10 is arranged in the second battery compartment 100B, the negative electrode tab connection portion 20 is the fourth battery compartment that is obliquely opposed to the second battery compartment. It is arranged in the battery compartment 100D. Further, as shown in FIG. 3C, when the positive electrode tab connection portion 10 is arranged in the third battery compartment 100C, the negative electrode tab connection portion 20 is the first battery compartment that is obliquely opposed to the third battery compartment. It is located at 100A. Then, as shown in FIG. 3D, when the positive electrode tab connection portion 10 is arranged in the fourth battery compartment 100D, the negative electrode tab connection portion 20 is the second battery compartment that is obliquely opposed to the fourth battery compartment. It is arranged at 100B.

The same applies even if the positive electrode side and the negative electrode side are viewed in reverse. When the negative electrode tab connection portion 20 is arranged in the first battery compartment 100A, the positive electrode tab connection portion 10 is arranged in the third battery compartment 100C located obliquely thereof (see FIG. 3C). When the negative electrode tab connection portion 20 is arranged in the second battery compartment 100B, the positive electrode tab connection portion 10 is arranged in the fourth battery compartment 100D located obliquely thereof (see FIG. 3D). When the negative electrode tab connection portion 20 is arranged in the third battery compartment 100C, the positive electrode tab connection portion 10 is arranged in the first battery compartment 100A located obliquely thereof (see FIG. 3A). When the negative electrode tab connection portion 20 is arranged in the fourth battery compartment 100D, the positive electrode tab connection portion 10 is arranged in the second battery compartment 100B located diagonally thereof (see FIG. 3B). ). As described above, in the secondary batteries according to FIGS. 3A to 3D, the section in which the positive electrode tab connection portion is arranged and the section in which the negative electrode tab connection portion is arranged are mutually arranged in a plan view. Except for the diagonally opposed forms, they are not adjacent to each other (they are not immediately adjacent to each other).

The first virtual equal bisected line 1 and the second virtual equal bisected line 2 that are orthogonal to each other are specifically intended for battery collision tests, and each is a virtual that evenly divides the dimensions of the battery or battery assembly into two equal parts. It is a line. That is, assuming the typical plan-view shape of the battery as shown in FIG. 2, the first virtual equal bisector 1 substantially has a dimension along one direction (for example, a dimension along the lateral direction). A virtual line that is evenly divided into two, that is, a bisector of one dimension. Similarly, the second virtual equal bisector 2 is a virtual line that substantially evenly bisects the dimension along the other direction (eg, the dimension along the vertical direction), that is, the dimension of the other. It is a bisector. Here, considering other than the above-mentioned typical shape of the secondary battery, the shapes shown in FIGS. 4 (B) to 4 (E) can be considered. In such a case, the smallest rectangle 30 including all the plan-view shapes (shapes excluding tabs) of the battery or the battery assembly is virtualized, and the horizontal and vertical uniform bisected lines are set as the first virtual uniform bisected line 1. And may be regarded as the second virtual equal bisected line 2. In summary, in the present invention, the "first virtual equal bisected line" and the "second virtual equal bisected line" include all the plan-view shapes (plan-view shapes excluding tabs and leads) of the battery or the battery assembly. However, when a square / rectangular rectangle having the smallest area is virtualized as a plan view, it corresponds to a vertical bisector in each of the horizontal and vertical dimensions of the rectangle (see FIG. 4).

Further, the "collision test" as used herein means a test in which a weight is naturally dropped to collide with a rod member placed on a battery as shown in FIG. Although not particularly limited, such a collision test may be a test based on the UL1642 Impact Test.

The tab connection portion is a portion in which tabs provided for a plurality of electrodes (particularly a plurality of the same electrodes) are connected to each other. Here, the "tab" referred to in the present invention is a member (15, 25) corresponding to a part of an electrode current collector (for example, a current collector foil) protruding from the side surface of the electrode assembly (right side view of FIG. 3). reference). That is, in the secondary battery, a current collector (for example, a current collector foil) provided on each of the plurality of electrodes of the positive electrode or the negative electrode extends so as to protrude from the side of the electrode assembly. The portion where the protruding current collectors are integrally aligned with each other corresponds to the tab connection portion. The positive electrode tab connecting portion 10 is a member in which the positive electrode tabs 15 provided for the plurality of positive electrodes are connected to each other. In some embodiments, all the tabs of the plurality of positive electrodes are connected to each other. Similarly, the negative electrode tab connection portion 20 is a member in which the negative electrode tabs 25 provided for the plurality of negative electrodes are connected to each other, and in some embodiments, all the tabs of the plurality of negative electrodes are connected to each other. When the current collector is a current collector foil, the tab connection portion corresponds to a portion where such current collector foils are aligned so as to collect each other. Therefore, the tab connection portion is referred to as a “foil collector”. You can also.

FIG. 6 shows one typical aspect of the present invention. In the secondary battery of the present invention, the positive electrode tab connection portion 10 in which the tabs provided for the plurality of positive electrodes (for example, the tabs provided for all the positive electrodes) are connected to each other and the plurality of negative electrodes are connected. The negative electrode tab connection portion 20 in which the provided tabs (for example, the tabs provided for all the negative electrodes) are connected to each other is the same and adjacent compartments in the four battery compartments (100A, 100B, 100C and 100D). Is not provided in. As can be seen from the illustrated embodiment, this means that the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are provided separately in two compartments that are obliquely opposed to each other.

A secondary battery having such a peculiar arrangement of tab connection portions is unlikely to generate excessive heat and / or ignite even if it is divided due to an external force such as a collision. That is, such a secondary battery is excellent in terms of safety in an actual usage environment, and moreover, in terms of safety as a used battery. In particular, even if the battery is accidentally or undesirably divided, the section in which the positive electrode tab connection portion is arranged and the section in which the negative electrode tab connection portion is arranged are separately separated from each other when the secondary battery is viewed in a plan view. The tendency to be divided increases. Here, in the case of such division, the positive electrode tab connection portion exists on one of the divided portions, and the negative electrode tab connection portion exists on the other divided portion. Therefore, the divided one and the other do not have a portion in which all the layers of the positive electrode and the negative electrode are electrically connected at the same time, respectively, and even if a part is internally short-circuited due to the division, all the layers are formed. Can result in a highly safe battery without a short circuit.

For a better understanding of the present invention, the embodiments shown in FIGS. 7 and 8 (A) to 8 (C) will be described. FIG. 7 shows an aspect in which the tab connection portion of the present invention is not arranged. Specifically, a positive electrode tab connection portion (for example, a positive electrode tab connection portion in which all positive electrode layers are electrically connected to each other) and a negative electrode tab connection portion (for example, a negative electrode in which all negative electrode layers are electrically connected to each other). Both of the tab connection portion) are arranged in the same compartment in the four battery compartments (100A, 100B, 100C and 100D). In the illustrated embodiment, both the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are arranged in the first electrode section 100A. In such a case, when an external force such as a collision acts and the portion is divided at the portion shown by the dotted line, both the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are present at the same time on one of the divided portions. Therefore, on one side, all layers of the positive electrode and the negative electrode are electrically connected. Therefore, if an internal short circuit occurs due to division, a large current tends to flow through the short circuit portion over all the layers in the end. .. That is, when a partial internal short circuit occurs, a discharge reaction proceeds between all the positive and negative electrodes facing each other, the current flows into the short circuit portion via the connection tab, and a large amount of Joule heat is generated at the short circuit portion. This is the case (see FIG. 15). Therefore, in the embodiment shown in FIG. 7, excessive ignition and / or heat generation is likely to occur in the divided secondary battery.

Similarly, in each of the embodiments of FIGS. 8A to 8C, the same inconvenient internal short circuit may occur. For example, in the embodiment shown in FIG. 8A, the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are arranged in compartments adjacent to each other, that is, in adjacent compartments. When it is divided by the horizontal dotted lines L1-L1', both the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are present at the same time on one of the divided lines. The same applies to the embodiment shown in FIG. 8 (B). When it is divided by the vertical dotted line L2-L2', both the positive electrode connection tab 10 and the negative electrode connection tab 20 are present at the same time on one of the divided lines. The plan view shape of the battery is not limited to a square or a rectangle, and is the same even in the case of a "non-rectangular" as shown in FIG. 8C, and is the same as the horizontal dotted line L3-L3'or the vertical dotted line L4-L4. When it is divided by ′, both the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are present at the same time on one of the divided portions. Therefore, in all of the embodiments shown in FIGS. 8A to 8C, if an internal short circuit occurs due to division, a large current may eventually flow to the short circuit portion over all layers, resulting in a large amount of Joule heat. Due to this, excessive ignition and / or heat generation is likely to occur.

In contrast to the embodiments shown in FIGS. 7 and 8 (A) to 8 (C) as described above, in the present invention, a portion in which all layers of the positive electrode and the negative electrode are electrically connected on one or the other divided portion is provided. Not held at the same time, all layers will not be short-circuited even if a part is internally short-circuited due to division. That is, even when such an internal short circuit occurs, an inconvenient phenomenon such as a large current flowing through the short circuit portion and a large amount of Joule heat is unlikely to occur.

One preferred embodiment of the present invention is shown in FIG. As can be seen from FIG. 6, the positive electrode tab connection portion 10 (for example, the positive electrode tab connection portion in which all the positive electrodes are electrically connected to each other) is connected to the first compartment 100A of the four battery compartments (100A, 100B, 100C and 100D). ) Is provided, while the negative electrode tab connection portion 20 (for example, the negative electrode tab connection portion in which all the negative electrodes are electrically connected to each other) is provided in the third section 100C, and the positive electrode tab connection portion 10 and the negative electrode are provided. The tab connection 20 is not provided in the "same and adjacent compartment". Further, in the present invention, the leads (60, 70) preferably have a peculiar arrangement structure in consideration of the tab connection portion.

Specifically, in the secondary battery of the present invention, at least one of the positive electrode tab connection portion and the negative electrode tab connection portion does not have a lead and does not form an external terminal of the secondary battery. That is, no lead is provided on one of the positive electrode tab connection portion and the negative electrode tab connection portion, or no lead is provided on both the positive electrode tab connection portion and the negative electrode tab connection portion. In other words, although one of the positive electrode tab connection portion and the negative electrode tab connection portion has a lead, both the positive electrode tab connection portion and the negative electrode tab connection portion do not have leads at the same time.

The term "lead" as used herein means, in a broad sense, a battery member for electrical connection, and in a narrow sense, a battery for electrical connection between an external terminal of a battery and an electrode assembly. It means a member. The lead is a member having conductivity. The reed is made of metal, for example, and preferably has a thin-walled form and / or a long form. Such leads may be those commonly used in secondary batteries (eg, lithium secondary batteries).

In the battery of the present invention, a first lead and a second lead may be provided as leads. Then, one of the first lead and the second lead may be connected to one of the positive electrode tab connection portion and the negative electrode tab connection portion. The tab connection portion connected to the lead becomes a member that directly contributes to the external terminal and contributes to the design of a suitable secondary battery. In this regard, in the secondary battery of the present invention, the other of the first lead and the second lead is one of the positive electrode and the negative electrode via another tab different from the tab at the positive electrode tab connection portion and the negative electrode tab connection portion. It is electrically connected to the electrode. In such a case, the electrode to which the "other" lead is electrically connected corresponds to an electrode on the opposite electrode side to the electrode to which the "one" lead is electrically connected. That is, the electrode to which the "other" lead is electrically connected corresponds to a different electrode with respect to the electrode at the positive electrode tab connection portion or the negative electrode tab connection portion to which the "one" lead is connected. In the present invention, the other of the first lead and the second lead can be provided at a position different from the installation position of the positive electrode tab connection portion and the negative electrode tab connection portion. The "further tabs (another tab different from the tabs at the positive electrode tab connection portion and the negative electrode tab connection portion)" referred to in the present specification is the number of tabs electrically connected to each other at the positive electrode tab connection portion. And / or may consist of fewer tabs than are electrically connected to each other at the negative electrode tab connection. In other words, at each of the positive and negative tab connections, more electrode layers than there are "further tabs" are electrically connected to each other (ie, "further tabs". It preferably consists of a larger number of tabs than a number).

In the exemplary embodiment shown in FIG. 6, the first lead 60 of the first lead 60 and the second lead 70 is connected to the positive electrode tab connecting portion 10. Then, the second lead 70 is electrically connected to the negative electrode via another tab 80 different from the current collecting tabs (15, 25) of the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20. As can be seen from the illustrated embodiment, the first lead 60 and the second lead 70 preferably have a positional relationship of being adjacent to each other in a plan view, and therefore are easily provided to the external terminal of the secondary battery. ..

Such a first lead and a second lead can work particularly advantageously for the secondary battery of the present invention, which has a unique arrangement mode of the positive electrode tab connection portion and the negative electrode tab connection portion. This is because the positive electrode tab connection portion and the negative electrode tab connection portion are not provided in the "identical and adjacent compartments", but when leads are provided in both the positive electrode tab connection portion and the negative electrode tab connection portion, the leads are arranged. This is because even the locations are limited to positional relationships that are not such “identical and adjacent compartments”. Therefore, in the lead installation mode as described above, the external terminals of the secondary battery can be arranged with a relatively high degree of freedom regardless of the arrangement mode of the positive electrode tab connection portion / negative electrode tab connection portion. In other words, it can be said that the external terminal of the secondary battery of the present invention can be provided at a desired position from the viewpoint of a control circuit (for example, a protection circuit and / or a charge / discharge control circuit) and space saving.

In the exemplary embodiment shown in FIG. 6, the positive electrode tab connecting portion 10 has a configuration in which all the tabs 15 of the plurality of positive electrodes are connected to each other. Similarly, the negative electrode tab connection portion 20 has a configuration in which all the tabs 25 of the plurality of negative electrodes are connected to each other. Therefore, all layers of the positive electrode and the negative electrode contribute to the charging / discharging of the battery, that is, the battery reaction. Here, with respect to the aspect of FIG. 6, even if an external force such as a collision acts to divide the line 1 along the first virtual equal bisected line 1, or the second virtual equal bisected line 2 is orthogonal to the line. Even if it is divided along the above, both the divided one and the other will not have a part where all the layers of the positive electrode and the negative electrode are electrically connected at the same time, and if a part is internally short-circuited due to the division. Even so, all layers will not be short-circuited in the end. That is, even when such an internal short circuit occurs, an inconvenient phenomenon such as a large current flowing through the short circuit portion and a large amount of Joule heat is unlikely to occur.

The present invention can be embodied in various aspects.

(First aspect)
A plan view of the electrode assembly according to the first aspect is shown in FIG. In such an embodiment, the negative electrode tab connecting portion 20 does not have a mode in which all of the plurality of negative electrodes are connected by the tabs 25. That is, some of the tabs provided on the plurality of negative electrodes are not provided to the negative electrode tab connection portion 20. In the secondary battery of the present invention, all the tabs do not necessarily have to be connected at each of the positive electrode tab connection portion and the negative electrode tab connection portion in this way.

In the exemplary embodiment of FIG. 9, even though not all of the plurality of negative electrodes are connected by the tabs 25 in the negative electrode tab connecting portion 20, the tabs (15, 25) of the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are different. Since another additional tab 80 is provided, all layers of the positive and negative electrodes contribute to the charging and discharging of the battery, that is, the battery reaction. In the embodiment shown in FIG. 9, one negative electrode comprises a tab 25 provided for the negative electrode tab connection 20 as well as another additional tab 80 connected to the lead, so that the negative electrode can be made through such a layer. All layers are electrically connected to each other.

Even if the secondary battery of the first aspect is divided along the first virtual equalization bisection line 1 by an external force such as a collision, or the secondary battery of the first aspect is divided into a second virtual equalization bidivision line 2 orthogonal to the line. Even if it is divided along, both the divided one and the other will not have a part where all the layers of the positive electrode and the negative electrode are electrically connected at the same time, and if a part is internally short-circuited due to the division. Even if there is, all layers will not be short-circuited in the end. That is, even when such an internal short circuit occurs, an inconvenient phenomenon such as a large current flowing through the short circuit portion and a large amount of Joule heat is unlikely to occur.

(Second aspect)
A plan view of the electrode assembly according to the second aspect is shown in FIG. In such an embodiment, there is one additional tab 80 connected to the lead (ie, "single").

In the secondary battery of the present invention, the number of additional additional tabs 80 connected to the leads (particularly, the number of tabs provided as the additional tabs or the tabs electrically connected to each other as additional tabs). The number of tabs (15, 25) may be smaller than the number of tabs (15, 25) in the positive electrode tab connection portion 10 and the negative electrode tab connection portion 20. For example, when the positive electrode tab connecting portion 10 has a form in which the tabs 15 of all layers of the positive electrode are connected to each other, a number of other additional positive electrode tabs 80 may be provided, which is smaller than the number of the tabs 15. Further, in the case where the tabs 15 of only some layers of the positive electrode are connected to each other in the positive electrode tab connection portion 10, the number of tabs 80 of another additional positive electrode is smaller than that of the several layers. It may be provided. The same applies to the case of the negative electrode. Even if the number of additional tabs 80 connected to the leads is small in this way, since the tabs of the positive electrode tab connection portion 10 and the negative electrode tab connection portion 20 are present, the entire layers of the positive electrode and the negative electrode are present. It can contribute to the charging and discharging of the battery, that is, the battery reaction.

When the number in "another additional positive electrode tab 80" is small, the number of layers that are finally short-circuited can be reduced even when a part of the battery is internally short-circuited due to the division of the battery. In particular, in the embodiment shown in FIG. 10, since the number of "another additional positive electrode tab 80" is one, the number of short circuits is minimized even when a part of the tabs is internally short-circuited due to the division of the battery. can do. That is, even if all the layers are not short-circuited due to division, if the number of "another further positive electrode tab 80" is large, the number of layers that are finally short-circuited may increase accordingly. In this regard, if the number of "another additional positive electrode tab 80" is one, the number of such short-circuited layers can be minimized, so that a large amount of Joule heat is less likely to be generated and is excessive. A secondary battery can be provided in which the risk of ignition and heat generation is more preferably prevented. In other words, a secondary battery with higher safety can be obtained.

(Third aspect)
FIG. 11 shows a plan view of the electrode assembly according to the third aspect. In such an embodiment, neither the positive electrode tab connecting portion 10 nor the negative electrode tab connecting portion 20 is provided with a lead. That is, both the first lead and the second lead are electrically connected to the positive electrode and the negative electrode, respectively, via another tab different from the tab at the positive electrode tab connection portion and the negative electrode tab connection portion.

More specifically, the first lead 60 is electrically connected to the positive electrode via "another additional tab 80A" different from the tab 15 of the positive electrode in the positive electrode tab connection portion 10, and the second lead 70 is connected. , The negative electrode tab connection portion 20 is electrically connected to the negative electrode via "another additional tab 80B" different from the tab 25 of the negative electrode.

In this embodiment, the so-called foil collecting portion and the external electrode extraction portion are completely separated on both the positive electrode side and the negative electrode side, so that the degree of freedom in the installation position of the external terminal of the secondary battery is higher. There is. That is, the external terminals can be particularly preferably arranged from the viewpoint of the control circuit (for example, the protection circuit and / or the charge / discharge control circuit) and the space saving.

(Fourth aspect)
A plan view of the electrode assembly according to the fourth aspect is shown in FIG. In such an embodiment, the plan view of the electrode assembly is non-rectangular. That is, the plan view shape of the secondary battery is "non-rectangular".

As used herein, the term "non-rectangular" refers to a shape in which the electrode shape in a plan view is not normally included in the concept of a square such as a square or a rectangle, and in particular, a part of such a square or a rectangle. It refers to a shape that lacks a part. Therefore, in a broad sense, "non-rectangular shape" refers to a shape in which the electrode shape in a plan view seen from above in the thickness direction is square and not rectangular, and in a narrow sense, the electrode shape in a plan view is a square / rectangle. It means that the shape is based on the above, but is partially notched from it (preferably the shape is notched at the corners of the square / rectangle of the base). As an example, "non-rectangular" is based on squares and rectangles whose electrode shapes in plan view are squares, rectangles, semicircles, semi-ovals, circles, etc. It may be a shape obtained by cutting out a part of an elliptical shape or a combination shape thereof from the base shape (particularly, a shape obtained by cutting out from a corner portion of the base shape) (see FIG. 13).

Even in the "non-rectangular" electrode assembly, the positive electrode tab connection portion 10 in which the tabs provided for the plurality of positive electrodes are connected to each other and the tabs provided for the plurality of negative electrodes are connected to each other. The negative electrode tab connection portion 20 is not provided in the same and adjacent compartments in the four battery compartments (100A, 100B, 100C and 100D). In the illustrated embodiment, the positive electrode tab connecting portion 10 and the negative electrode tab connecting portion 20 are provided separately in two compartments that are obliquely opposed to each other. Therefore, even if an external force such as a collision acts to divide the battery along the first virtual equal bisected line 1, or the battery is divided along the second virtual equal bisected line 2 orthogonal to it. However, in both the divided one and the other, all the layers of the positive electrode and the negative electrode do not have a portion electrically connected at the same time, and even if a part is internally short-circuited due to the division, all the layers are formed. There is no short circuit in the end. That is, even when such an internal short circuit occurs, an inconvenient phenomenon such as a large current flowing through the short circuit portion and a large amount of Joule heat is unlikely to occur (see FIG. 14).

In the "non-rectangular" aspect, the first virtual equal bisected line 1 and the second virtual equal bisected line 2 are considered to be lines based on the base square / rectangle that is assumed to be before the notch. May be good. That is, the first virtual evenly divided line 1 substantially measures the dimensions along one direction (for example, the dimensions along the lateral direction) with respect to the square / rectangle of the base that is assumed to be before the notch in the plan view shape. The line may be evenly divided into two. Similarly, the second virtual even bisected line 2 is a dimension along the other direction (for example, a dimension along the vertical direction) with respect to the base square or rectangle that is assumed to be before the notch in the plan view shape. It may be a line that divides the line into two substantially evenly.

In the aspect shown in FIG. 12, the "another additional tab" to which the leads are connected is a tab provided to the electrode corresponding to the outermost layer of the electrode in the electrode assembly. Specifically, an "another additional tab 80" on the outermost layer of the electrode is connected to the first lead 60. As described above, in the secondary battery of the present invention, the first lead or the second lead connected via another additional tab is electrically connected only to the electrode corresponding to the outermost layer of the electrode in the electrode assembly. You can. This is preferable in that when the battery is divided due to an impact or the like, the electrodes of the outermost layer thereof are divided relatively early. This is because if the electrodes in the outermost layer of the electrodes are divided relatively quickly in this way, the amount of heat generated in the time until the electrodes are completely divided can be further suppressed, and as a result, a battery with higher safety. Can be brought about.

From this point of view, the outermost electrode layer is preferably the outermost electrode layer on the side that collides relatively early. That is, in the secondary battery of the present invention, the outermost layer of the electrode may be only one of the two outermost layers in the stacking direction of the electrode assembly.

Although the embodiments of the present invention have been described above, they merely exemplify typical examples. Therefore, those skilled in the art will easily understand that the present invention is not limited to this, and various aspects are conceivable.

For example, in the above description, the mode of electrical connection between the outermost electrode layer and the lead is described based on the “non-rectangular” electrode assembly shown in FIG. 12, but it is a square or rectangular electrode assembly. The same is true. That is, in a square / rectangular electrode assembly in a plan view, the first lead or the second lead connected via "another additional tab" is electrically connected only to the electrode corresponding to the outermost layer of the electrode. You may be.

The secondary battery according to the embodiment of the present invention can be used in various fields where storage is expected. Although only an example, secondary batteries are used in the fields of electricity, information, and communication (for example, mobile phones, smart watches, smartphones, laptop computers, digital cameras, activity meters, arm computers, and electronic devices) in which mobile devices are used. Mobile device fields such as paper), home / small industrial applications (eg, power tools, golf carts, home / nursing / industrial robot fields), large industrial applications (eg, forklifts, elevators, bay port cranes) ), Transportation system field (for example, hybrid car, electric car, bus, train, electric assist bicycle, electric motorcycle, etc.), power system application (for example, various power generation, road conditioner, smart grid, general household installation type power storage system) Fields such as), medical applications (medical equipment fields such as earphone hearing aids), pharmaceutical applications (fields such as dose management systems), IoT fields, and space / deep sea applications (for example, space probes, submersible research vessels, etc.) It can be used for fields).

1 1st virtual equal bisected line 2 2nd virtual even bisected line 3 Positive electrode 4 Negative electrode 5 Separator 8 Electrode constituent layer 10 Positive electrode tab connection part 15 tabs (Positive tabs that are matched to each other as positive electrode connection tabs)
20 Negative electrode tab connection part 25 tab (Negative electrode tab that can be matched with each other as a negative electrode connection tab)
30 Virtual rectangle 60 1st lead 70 2nd lead 80 Another additional tab 80A Further tab on the positive electrode side 80B Further tab on the negative electrode side 100 Electrode assembly 100A 1st battery compartment 100B 2nd battery compartment 100C 3rd battery Partition 100D 4th battery compartment

Claims (9)

A secondary battery comprising an electrode assembly comprising a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode.
It has a positive electrode tab connection portion in which tabs provided for the plurality of positive electrodes are connected to each other, and a negative electrode tab connection portion in which tabs provided for the plurality of negative electrodes are connected to each other.
In the plan view of the secondary battery, when four battery compartments divided by the first virtual equalization bisection line and the second virtual equalization dichotomy line orthogonal to each other are virtualized, the positive electrode tabs are placed in the same compartment and adjacent compartments. The tab connection portion is arranged so that both the connection portion and the negative electrode tab connection portion do not exist.
A secondary battery in which at least one of the positive electrode tab connection portion and the negative electrode tab connection portion does not have a lead and is not provided to an external terminal of the secondary battery. The secondary battery according to claim 1, wherein in the positive electrode tab connection portion, all the tabs of the plurality of positive electrodes are connected to each other. The secondary battery according to claim 1 or 2, wherein in the negative electrode tab connection portion, all the tabs of the plurality of negative electrodes are connected to each other. It consists of a first lead and a second lead as the leads.
The secondary battery according to any one of claims 1 to 3, wherein one of the first lead and the second lead is connected to one of the positive electrode tab connection portion and the negative electrode tab connection portion. The first lead and the other of the second leads are electrically connected to one electrode of the positive electrode and the negative electrode via another tab different from the tab of the positive electrode tab connection portion and the negative electrode tab connection portion. The secondary battery according to claim 4, which is connected. It consists of a first lead and a second lead as the leads.
Both the first lead and the second lead are electrically connected to the positive electrode and the negative electrode, respectively, via another tab different from the tab in the positive electrode tab connection portion and the negative electrode tab connection portion. The secondary battery according to any one of claims 1 to 3. The secondary battery according to claim 5 or 6, wherein the number of the additional tabs is smaller than the number of the tabs in each of the positive electrode tab connection portion and the negative electrode tab connection portion. Claims 4 to 7 wherein the first lead or the second lead connected via the additional tab is electrically connected to an electrode corresponding to the outermost layer of the electrode in the electrode assembly. The secondary battery described in any of. The secondary battery according to any one of claims 1 to 8, wherein the electrode of the electrode assembly includes a positive electrode and a negative electrode capable of storing and releasing lithium ions.

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