WO2021006161A1 - Secondary battery - Google Patents

Abstract

Provided is a secondary battery comprising an electrode assembly including a positive electrode, a negative electrode and a separator disposed therebetween. The positive and negative electrodes of the secondary battery each have: an electrode layer in which an electrode material is formed on a current collector; and a current collection layer at which the current collector is exposed. At least one electrode from between the positive electrode and the negative electrode includes an electrode unit that comprises: multiple electrode layers facing the other electrode; and a connection part that electrically connects the multiple electrode layers. In a cross-sectional view of the secondary battery, the connection part is located on a side of the other electrode. The positive electrode and the negative electrode are configured to collect the current in the current collection layer which is close to the electrode layer.

Description

Rechargeable battery

The present invention relates to a secondary battery.

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.

The secondary battery generally has a structure in which the electrode assembly is housed inside the exterior.

Japanese Unexamined Patent Publication No. 2005-243455

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

A secondary battery generally has a structure in which an electrode assembly including a positive electrode, a negative electrode, and a separator between the electrodes is enclosed in an outer body. In the electrode assembly, the meanderingly bent electrode is connected to the electrode terminal only via a current collector provided at the electrode end (for example, Patent Document 1). That is, assuming a state in which the electrodes of the electrode assembly are expanded into a non-bent state, current collection is performed from only one end of the electrode, which has a short dimension.

In the exemplary embodiment shown in FIG. 16, the secondary battery 400 generally includes an electrode assembly 200 including a positive electrode 10A, a negative electrode 10B, and a separator 20 arranged between the positive electrode 10A and the negative electrode 10B, and an electrolyte. It has a structure enclosed in the exterior body 300. The positive electrode 10A is composed of a positive electrode current collector 1A and a positive electrode material 2A. Further, the negative electrode 10B is composed of a negative electrode current collector 1B and a negative electrode material 2B. Positive 10A and the negative electrode 10B are electrode through a current collector of the electrode end that is positioned an upper major surface and a lower major surface of the electrode assembly 200 1A _E and 1B _E respectively only terminals (i.e., outer package 300A and 300B) Is connected to.

In the secondary battery 400 having such a configuration, in both of the positive electrode and the negative electrode also, electron transfer is performed through each folded current collector positioned at the outermost end of the electrode 1A _E and 1B _E only Therefore, the conduction distance is long and the electric resistance may increase.

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 having a lower resistance while maintaining a high battery capacity.

The present invention is a secondary battery comprising an electrode assembly including a positive electrode, a negative electrode and a separator arranged between the positive electrode and the negative electrode, wherein the electrodes of the positive electrode and the negative electrode are placed on a current collector. It has an electrode layer on which an electrode material is formed and a current collector layer in which the current collector is exposed, and at least one of the positive electrode and the negative electrode has a plurality of electrode layers facing the other electrode and the plurality of electrode layers. It includes an electrode unit including a connecting portion that electrically connects the electrode layers, the connecting portion is positioned to the side of the other electrode in a cross-sectional view of the secondary battery, and the positive electrode and the negative electrode are close to the electrode layer. The present invention relates to a secondary battery that collects electricity in the current collecting layer.

The secondary battery according to the present invention has a structure having a lower resistance while maintaining a high battery capacity.

Specifically, a secondary battery having a structure in which a plurality of electrode layers are connected to each other at at least one electrode of a positive electrode and a negative electrode has a structure in which current is collected by a current collecting layer close to the electrode layer. More specifically, the current may be collected from the current collecting layer adjacent to each of the plurality of electrode layers connected to each other at the electrode. Therefore, in the secondary battery according to the present invention, the conduction distance can be shortened. Therefore, it is possible to realize a secondary battery having a lower resistance while maintaining a high battery capacity.

1A to 1D are schematic plan views showing various embodiments of electrodes in a secondary battery according to an embodiment of the present invention. FIG. 2 is a schematic plan view showing the movement of electrons in the electrode unit. 3A and 3B are schematic plan views showing an embodiment of an electrode unit in which the electrode layer has various shapes (FIG. 3A: substantially circular shape, FIG. 3B: substantially square shape). FIG. 4 is a schematic plan view showing an embodiment of a positive / negative electrode body including the electrode unit shown in FIG. 3A. 5A and 5B are schematic plan views showing an embodiment of an electrode unit and a positive electrode body having a connecting portion provided in a single shape so as to straddle each of the electrode layers (FIG. 5A: substantially circular). Shape, FIG. 5B: substantially square shape). 6A and 6B are schematic plan views showing an embodiment of an electrode unit and a positive electrode body having a structure for collecting current at a portion other than the connecting portion (FIG. 6A: substantially circular shape, FIG. FIG. 6B: substantially square shape). 7A and 7B are schematic plan views showing an embodiment of a plurality of electrode units in which the electrode layers have various shapes (FIG. 7A: substantially circular shape, FIG. 7B: substantially square shape). FIG. 8 is a schematic plan view showing an embodiment of a positive / negative electrode body including the electrode unit shown in FIG. 7A. FIG. 9 is a schematic plan perspective view showing an embodiment of the secondary battery using the positive and negative electrodes of FIG. 4. 10A and 10B are schematic cross-sectional views of the secondary battery shown in FIG. 9 (FIG. 10A: cross section along line aa', FIG. 10B: cross section along line bb'). 11A and 11B are schematic cross-sectional views showing another embodiment of the secondary battery shown in FIG. 9 (FIG. 11A: cross section along line aa', FIG. 11B: line bb'. Cross section along). FIG. 12 is a schematic plan perspective view showing another embodiment of the secondary battery using the positive electrode body of FIG. 4. 13A and 13B are schematic cross-sectional views of the secondary battery shown in FIG. 12 (FIG. 13A: cross section along line aa', FIG. 13B: cross section along line bb'). FIG. 14 is a schematic plan perspective view showing a secondary battery using the positive and negative electrodes of FIG. 8. 15A and 15B are schematic cross-sectional views of the secondary battery shown in FIG. 14 (FIG. 15A: cross section along line aa', FIG. 15B: cross section along line bb'). FIG. 16 is a schematic cross-sectional view showing a secondary battery according to the prior art.

[Characteristics of the secondary battery according to the present invention]
The secondary battery according to the present invention is a secondary battery having a configuration in which a plurality of electrode layers are connected to each other at at least one electrode of a positive electrode and a negative electrode, and is characterized in that it has a structure for collecting electricity at the electrodes. ..

Specifically, in the secondary battery of the present invention, the positive electrode and the negative electrode of the present invention each have an electrode layer in which an electrode material is formed on the current collector and a current collector layer in which the current collector is exposed. Here, the electrode layer and the current collector layer are positioned close to each other.

At least one of the positive electrode and the negative electrode has an electrode unit including a plurality of electrode layers facing the other electrode and a connecting portion for electrically connecting the plurality of electrode layers to each other.

In the configuration as described above, preferably, each electrode of the positive electrode and the negative electrode has a structure in which current is collected by a current collecting layer close to the electrode layer. More specifically, for example, in each electrode of the positive electrode and the negative electrode, current collection may be performed via a current collector layer adjacent to each of the plurality of electrode layers. That is, in a plan view in which the positive electrode and negative electrode electrodes are expanded, current collection may be performed so that each current collecting layer adjacent to each of the plurality of electrode layers serves as an output tab (see FIG. 2 to be referred to later). ).

By providing an electrode unit in which the electrode layers are connected to each other, it becomes easy to save space in the secondary battery. That is, a more compact electrode assembly can be preferably obtained, and the overall volume of the secondary battery can be reduced. Further, since the electrode provided by being bent can collect current in the current collecting layer close to the electrode layer, the conduction distance can be shortened. Therefore, it is possible to obtain a secondary battery having a lower resistance while maintaining a high battery capacity.

The "secondary battery" in the present specification refers to a battery that can be repeatedly charged and discharged. The "secondary battery" is not overly bound by its name and may include, for example, a "storage device".

The "electrode layer" in the present specification refers to a layer formed by forming an electrode material on a current collector in an electrode. In other words, the "electrode layer" refers to a layer of an electrode containing a current collector and an electrode material formed on the current collector. Such an electrode layer corresponds to a layer that functions as an electrode (that is, a layer that contributes to the transfer of ions and electrons).

The "current collector layer" in the present specification refers to a portion of the electrode where the current collector is exposed. In other words, the "current collector layer" refers to a portion of the electrode where no electrode material is formed on the current collector. Therefore, in the present invention, the current collector layer can also be referred to as a current collector.

[Structure of a secondary battery according to the present invention]
Hereinafter, the secondary battery of the present invention will be described in detail with reference to drawings showing some embodiments, but various elements in the drawings are merely schematically and exemplified for the understanding of the present invention. However, the appearance and dimensional ratio may differ from the actual product.

The "thickness" direction described directly or indirectly in the present specification is based on the direction in which the electrode materials constituting the secondary battery are stacked (or the direction in which they are stacked). The stacking direction of the electrode material corresponds to the thickness direction. For example, in the case of a "secondary battery having a plate-like thickness" such as a flat battery, the thickness direction corresponds to the plate thickness direction of the secondary battery.

The "planar view" referred to in the present specification is based on a form in which an object is viewed from above or below along the thickness direction. In short, it is based on the planar form of the object shown in FIG.

Further, the "cross-sectional view" referred to in the present specification is a form when the object is captured from a direction substantially perpendicular to the thickness direction (in other words, a form when the object is cut out on a plane parallel to the thickness direction). Is based on. In short, it is based on the shape of the cross section of the object shown in FIG.

The secondary battery of the present invention houses the electrode assembly and the electrolyte inside the exterior. The electrode assembly is formed by alternately stacking positive electrodes and negative electrodes via separators.

The electrodes of the positive electrode and the negative electrode each have an electrode layer in which an electrode material is formed on the current collector and a current collector layer in which the current collector is exposed. Here, the electrode layer and the current collector layer are positioned close to each other. Further, at least one of the electrodes has an electrode unit including a plurality of electrode layers and a connecting portion for electrically connecting the plurality of electrode layers to each other.

In the exemplary embodiment shown in FIG. 1, the positive electrode 10A includes a positive electrode layer 11A in which a positive electrode material (not shown) is formed on the positive electrode current collector 1A, and a positive electrode current collector layer 12A in which the positive electrode current collector 1A is exposed. Has. More specifically, for example, the positive electrode current collector layer 12A may be provided by partially exposing the positive electrode current collector 1A contained in the positive electrode layer 11A so as to protrude from the positive electrode layer 11A.

Moreover, the negative electrode 10B includes a negative electrode unit 10B _U comprising a negative electrode connecting portion 13B for electrically connecting the plurality of negative electrode layer 11B and the plurality of negative electrode layer 11B. More specifically, for example, in the negative electrode 10B, with respect to the plurality of negative electrode layers 11B, the negative electrode layers adjacent to each other or adjacent to each other are directly connected by the connecting portion 13B. In other words, the negative electrode unit 10B _U, each of the plurality of negative electrode layer 11B is thereto provided with a negative electrode connecting portion for directly connecting. As can be seen from the exemplary embodiment shown in FIG. 1, the negative electrode current collector layer 12B obtained by partially exposing the negative electrode current collector 1B may form the connecting portion 13B.

Such a connecting portion is a portion that connects the electrode layers adjacent to each other. The connecting portion is composed of current collectors of electrode layers adjacent to each other, and the portion where the polar material layer is not provided, that is, the uncoated portion in which the polar material material is not applied to the current collector. May correspond to.

In particular, in the electrode unit, the connecting portion may be provided so as to be directly connected to the electrode layers adjacent to each other. That is, the connecting portion may be shared by the connecting portion extending from one of the electrode layers adjacent to each other and the connecting portion extending from the other of the electrode layers adjacent to each other. The connecting portion may be, for example, a portion positioned between two electrode layers adjacent to each other (see FIGS. 1 and 3 and the like). That is, in a plan view in which the electrode unit is developed, a connecting portion (for example, composed of a current collector of each electrode layer and not provided with a polar material layer) provided between two electrode layers adjacent to each other is provided. The connecting portion) to be formed may be positioned so as to project directly from the electrode layer from one of the two electrode layers toward the other. Alternatively, the connecting portion may be a portion provided in a single shape so as to straddle each of the two or more or three or more electrode layers (see FIG. 5). That is, in a plan view in which the electrode unit is developed, it is provided because it is composed of a connecting portion (for example, a current collector of each electrode layer and is not provided with a polar material layer) provided between electrode layers adjacent to each other. The connecting portion) may be continuously provided not only between the electrode layers but also in a plan view as shown in FIG. 5 so as to partially overlap the electrode layer.

In a plan view in which the electrode unit is deployed, the connecting portions may be aligned or extended in a straight line. That is, the plurality of connecting portions 13A or 13B provided on the electrode unit as shown in FIG. 3 may be arranged along a straight line with each other, and the electrode unit as shown in FIG. 5 may be arranged. The single connecting portion 13A or 13B may extend linearly as a whole. As shown, in the unfolded plan view of the electrode unit, such connecting portions may be linearly aligned or extended at positions deviated from the center of each of the electrode layer or the plurality of electrode layers. As described above, the linearly aligned or extending connecting portions contribute to more uniform current collection as a whole and contribute to the realization of a more suitable secondary battery.

In the unfolded plan view of the electrode unit, the width direction dimension of the connecting portion is smaller than the maximum width direction dimension of the electrode layer in contact with the connecting portion. In terms of exemplary embodiments shown in FIGS. 1A and FIG. 1D, the negative electrode unit 10B _U, the width dimension _{J W} of the negative electrode connecting portion 13B, rather than the maximum width dimension _{E W} of the negative electrode layer 11B in contact with the negative electrode connecting portion 13B It's getting smaller.

The connecting portion does not have to have an electrode material formed. In other words, the connecting portion may consist of a current collector layer. That is, the connecting portion may be, for example, a portion substantially composed of only the current collector layer. As an alternative aspect, the connecting portion may be formed with an electrode material. Speaking in an illustrative embodiment shown in FIG. 1A, in the negative electrode unit 10B _U, the negative electrode connecting portion 13B is comprised only the anode current collector layer 12B. That is, in this case, the connecting portion and the current collecting layer are substantially synonymous.

It is preferable that no electrode material is formed on the connecting portion so that the structure can collect current at the connecting portion. Further, from the viewpoint of facilitating the manufacturing process, it is preferable that no electrode material is formed on the connecting portion.

The electrode unit may include at least two electrode layers and may include three or more electrode layers. In the case of three or more electrode layers, the electrode unit may include a plurality of connecting portions between the electrode layers. From the viewpoint of increasing energy density and the like, the number of electrode layers in the electrode unit is preferably four or more.

The number of electrode layers in the electrode unit is the number per one side of the current collector. The electrode unit includes two or more electrode layers formed via a connecting portion on both sides of the current collector. In this case, the number, arrangement and dimensions of the electrode layers on the front and back of the current collector are usually the same.

That is, each electrode layer on the other surface is formed directly below or directly above the region where each electrode layer on one surface of the current collector is formed via the current collector. All of the electrode layers of one electrode unit have the same polarity.

In the secondary battery of the present invention, at least one of the positive electrode and the negative electrode contains an electrode unit. In such a case, the electrode may include at least one electrode unit having two electrode layers and a connecting portion between them, and thus may include a plurality of such electrode units. For example, when the positive electrode includes an electrode unit, the unit on the positive electrode side may be provided as a plurality of electrode units. Similarly, when the negative electrode includes an electrode unit, the unit on the negative electrode side may be provided as a plurality of electrode units.

In terms of exemplary embodiment illustrated, the negative electrode 10B is a negative electrode unit 10B _U with two negative electrode layer 11B may include one (see FIG. 1A), (see FIG. 1B) may not more contain three It may contain a negative electrode unit 10B _U having the above negative electrode layer 11B (see FIG. 1C).

The electrode layer in the electrode unit may have a circular shape (see FIGS. 1A to 1C), a quadrangular shape (see FIG. 1D), or another irregular shape in a plan view. The "circular shape" here is not limited to a perfect circle, but means a shape that can be included in the concept of a circle in the broadest sense, including an ellipse or an oval shape (in short, a circle is a circle). It may be shaped as if it were formed primarily or mostly based on a curve). Similarly, the term "quadrangle" as used herein means a substantially quadrangle, and is therefore broadly interpreted to include squares, rectangles, parallelograms, trapezoids, and the like.

In the secondary battery according to the present invention, the positive electrode and the negative electrode have a structure in which current is collected by a current collecting layer close to the electrode layer. Further, when the electrode includes an electrode unit, it has a structure in which current is collected by a current collecting layer adjacent to at least two electrode layers. That is, when the positive electrode has an electrode unit, current collection is performed via a current collecting layer (for example, a connecting portion) adjacent to each of the at least two positive electrode layers, and when the negative electrode has an electrode unit, at least two negative electrode layers are collected. The current is collected through the current collecting layer (for example, the connecting portion) adjacent to each of the above.

In the broad sense, "collecting current in an adjacent current collecting layer" as used herein means that each of the electrode layers included in the electrode unit collects electricity from an adjacent current collecting layer directly connected to the electrode unit. It means that it will be done. In a narrow sense, "collecting current in an adjacent current collecting layer" means that, in a plan view of the electrode unit shown in FIG. 2, it is directly applied to each of the plurality of electrode layers included in the unit. It means that the current is collected through each current collecting layer which is provided and adjacent to each of the electrode layers. That is, in the electrode unit shown in FIG. 2, there are a plurality of places where current is collected, not a single place. More specifically, the electrode unit 10 _u shown in FIG. 2 has a structure in which current is collected by a current collecting layer 12 (that is, a connecting portion 13) adjacent to each of the electrode layers 11. The arrows in FIG. 2 schematically show the flow of electrons. That is, in such an electrode unit, if there are N electrode layers included in the unit in a plan view, current collection may be performed from a plurality of N-1 locations.

As can be seen from the illustrated embodiment, in the electrode unit including a plurality of electrode layers, each connecting portion located between the electrode layers adjacent to each other may form an output tab. That is, in the electrode unit including the plurality of electrode layers, the current may be collected from the positions of the connecting portions located between the electrode layers adjacent to each other to output to the outside. The location of each connecting portion located between the electrode layers adjacent to each other may correspond to a bent portion in the electrode assembly. Therefore, current collection may be performed from each of the bent portions. In some preferred embodiments, the connecting portions located between such adjacent electrode layers may be welded together. This is because the degree of freedom in designing the output to the outside can be improved.

With the above configuration, the positive electrode and negative electrode can collect current through the current collecting layer as close as possible to the electrode layer, and the conduction distance can be shortened. Thereby, it is possible to obtain a secondary battery having a lower resistance while maintaining a high battery capacity. More specifically, as can be seen from the exemplary embodiment shown in FIG. 2, the distance through which electrons flow can be shortened, and low resistance is likely to be brought about during high-speed charging.

Further, assuming that the electrodes are provided with three or more electrode layers, current collection is performed in each current collector layer close to each electrode layer, so that the occurrence of current concentration can be prevented.

In one embodiment, both the positive and negative electrodes include electrode units. Speaking in an illustrative embodiment shown in FIG. 3, the positive electrode 10A includes a positive electrode units 10A _U including a plurality of positive electrode connecting portion 13A for connecting a plurality of the positive electrode layer 11A and the plurality of positive electrode layer 11A electrically to each other. Moreover, the negative electrode 10B includes a negative electrode unit 10B _U provided with a plurality of negative electrode connecting portion 13B which connects a plurality of negative electrode layer 11B and the plurality of negative electrode layer 11B electrically to each other.

In the production of the electrode assembly, first, the positive and negative electrodes are prepared by laminating the positive electrode and the negative electrode as described above via a separator. More specifically, a positive electrode body in which a positive electrode layer in a positive electrode and a negative electrode layer in a negative electrode are laminated via a separator is prepared.

A positive electrode body is a precursor of an electrode assembly capable of forming an electrode assembly by self-bending (particularly, bending of one or more current collector layers / connecting portions), and is one or more electrodes. Includes units. That is, the positive electrode body may include one or more of the positive electrode unit and the negative electrode unit.

Here, "bending" includes bending in a bay shape (or bow shape) (that is, bending in a substantially curved line) and bending at an acute angle (that is, bending in a substantially straight line). In the present invention, the bending is particularly intended to bend the current collector layer / connecting portion.

When only one of the positive electrode and the negative electrode has an electrode unit (see FIG. 1), the electrode layer of one electrode is superposed on the electrode layer of the other electrode via a separator.

In the exemplary embodiment shown in FIG. 1C, the positive electrode layer 11A ₁ is superposed on _one of the opposing surfaces of the negative electrode layer 11B ₁ via a separator, and the positive electrode layer 11A ₂ is adjacent to the negative electrode layer 11B _{1 in} the longitudinal direction L. It is superposed on the other facing surface of the negative electrode layer 11B ₂ arranged so as to be interposed via a separator. The positive electrode layer 11A ₃ and the negative electrode layer 11B ₃ and the positive electrode layer 11A ₄ and the negative electrode layer 11B ₄ are also superposed in the same manner.

When both the positive electrode and the negative electrode have electrode units (see FIG. 4 and the like), the positive electrode layer and the negative electrode layer in each electrode unit are superposed so as to be alternately overlapped with each other via a separator. That is, the electrode units are entirely overlapped with each other so that the positive electrode layers of the electrode unit on the positive electrode side and the negative electrode layers of the electrode unit on the negative electrode side are overlapped with each other via the separators.

Speaking in an illustrative embodiment shown in FIG. 4, the positive and negative electrode body 100 includes a positive electrode units 10A _u and the negative electrode unit 10B _u shown in FIG. 3A.

The positive electrode unit 10A _u has four positive electrode layer 11A _{(i.e., 11A 1, 11A 2, 11A} 3 and 11A _4). Each positive electrode layer 11A is electrically connected by _three positive electrode connecting portions 13A (that is, 13A ₁ , 13A ₂ and 13A ₃ ), respectively.

Similarly, the negative electrode unit 10B _u has four negative electrode layer 11B _{(i.e., 11B 1, 11B 2, 11B} 3 and 11B _4). Each negative electrode layer 11B is electrically connected by _three negative electrode connecting portions 13B (that is, 13B ₁ , 13B ₂ and 13B ₃ ), respectively.

In the positive electrode body 100, the positive electrode layers 11A and the negative electrode layers 11B are overlapped with each other so as to be alternately overlapped with each other via a separator. In FIG. 4, the separator between the electrode layers is omitted.

As described above, the positive and negative electrode bodies 100 include both the positive and negative electrode units, so that the alignment between the positive electrode layer 11A and the negative electrode layer 11B can be facilitated. Specifically, since the positive electrode layers 11A and the negative electrode layers 11B can be alternately overlapped with each other, the movement between the electrode layers can be mutually suppressed. Therefore, the positional deviation between the electrode layers can be prevented.

In the width direction W of the positive electrode body 100, the positive electrode connecting portion 13A is deviated to one side with respect to the central axis of the positive electrode body 100. More specifically, in the plan view of the positive electrode body 100, the positive electrode connecting portion 13A is positioned at a position away from the central axis xx'of the positive electrode body 100. In the plan view shown in FIG. 4, it can be said that the plurality of positive electrode connecting portions 13A are linearly aligned at positions separated from the central axis xx'.

Further, in the width direction W of the positive electrode body 100, the negative electrode connecting portion 13B is deviated from the central axis of the positive electrode body 100 to the side opposite to the positive electrode connecting portion 13A. More specifically, in the plan view of the positive and negative electrode body 100, the negative electrode connecting portion 13B is positioned at a position away from the central axis xx'of the positive and negative electrode body 100 and on the side opposite to the positive electrode connecting portion 13A. ing. In the plan view shown in FIG. 4, it can be said that the plurality of negative electrode connecting portions 13B are linearly aligned at positions separated from the central axis xx'.

In one embodiment, in a positive electrode body, an electrode having at least one of the positive electrode and the negative electrode provided in a single shape so as to straddle each of three or more electrode layers and the electrode layers. Includes units (see Figure 5). Here, "single form" means that the connecting portion consists of one region that is not separated by the electrode layer.

Speaking in an illustrative embodiment shown in FIG. 5A, the positive electrode connecting portion 13A of the positive electrode unit 10A u _'is provided in a single shape so as to extend to one end of the periphery of the plurality of positive electrode layer 11A. It can be said that the single positive electrode connecting portion 13A extends long along one end of the peripheral edge of the plurality of positive electrode layers 11A. The same applies to the negative electrode unit 10B _u '. In other words, the negative electrode connecting portion 13B in the anode unit 10B u _'is provided in a single shape so as to extend to one end of the periphery of the plurality of negative electrode layer 11B. It can be said that the single negative electrode connecting portion 13B extends long along one end of the peripheral edge of the plurality of negative electrode layers 11B.

With the above configuration, the alignment between the electrode units becomes easier. Further, when the electrode layer is applied on the current collector, the number of times of application can be reduced. Thereby, the manufacturing process can be particularly facilitated.

Further, when the electrode unit collects current at the connecting portion, the contact area between each electrode layer and the connecting portion can be increased. Therefore, a secondary battery having a particularly low resistance can be easily realized.

In the present embodiment, the connecting portion may be provided in a single shape so as to straddle at least two electrode layers. From the viewpoint of facilitating the manufacturing process and reducing the resistance, it is preferable that the connecting portion is provided in a single shape so as to straddle all the electrode layers.

In one embodiment, the current collector layer that collects current in the electrode unit forms a connecting portion as in the above-described embodiment (see FIGS. 4 and 5 and the like). That is, current collection may be performed from a current collector layer having the form of a connecting portion that connects the electrode layers adjacent to each other.

More specifically, in the positive electrode units 10A _u and 10A _u 'shown in FIGS. 4 and 5, the positive electrode layer 11A ₁ performs current collection at collector layer 12A ₁ adjacent to the positive electrode layer 11A _1. The positive electrode layer 11A ₂ collects current in the current collecting layers 12A ₁ and 12A ₂ adjacent to the positive electrode layer 11A ₂ . The positive electrode layer 11A ₃ collects current in the current collecting layers 12A ₂ and 12A ₃ adjacent to the positive electrode layer 11A ₃ . Further, the positive electrode layer 11A ₄ collects current in the current collecting layer 12A ₃ close to the positive electrode layer 11A ₄ . Even in the negative electrode unit 10B _u and 10B _u ', is the same. In this way, current collection is performed via each current collector layer provided as a connecting portion adjacent to each electrode layer.

With the above-mentioned configuration, the number of members used for the electrode assembly can be minimized, and the secondary battery can easily bring about high energy density and / or space saving.

In another embodiment, the current collecting layer for collecting current in the electrode unit is formed of a portion other than the connecting portion. In the exemplary embodiment shown in FIG. 6A, the positive electrode unit 10A _u ″ has the positive electrode current collector 1A and two or more positive electrode layers 11A formed on the positive electrode current collector 1A via the positive electrode connecting portion 13A. Have.

The positive electrode unit 10A _u '' also has a positive electrode current collecting layer 12A in close proximity to the positive electrode layer 11A. Here, the positive electrode current collector layer 12A is provided as a positive electrode protruding portion 14A different from the connecting portion. The positive electrode projecting portion 14A may project in a direction substantially orthogonal to the direction in which the plurality of positive electrode layers 11A are aligned in a plan view in which the electrode unit as shown in FIG. 6A is developed. The positive electrode unit 10A _u '' has a structure in which current is collected by the positive electrode current collecting layer 12A different from the connecting portion. Similarly, the negative electrode unit 10B u _'' performs current collection at the negative electrode collector layer 12B provided as different negative electrode protrusion 14B and the connecting part. Even in the negative electrode unit 10B _u '', the negative electrode protruding portion 14B protrudes in a direction substantially orthogonal to the direction in which the plurality of negative electrode layers 11B are aligned in a plan view in which the electrode unit is developed as shown in FIG. 6A. Good.

More specifically, in the positive electrode unit 10A _{u '',} the positive electrode layer _{11A 1, 11A 2, 11A 3} and 11A ₄ are positive collector layer _12A 1 adjacent to their respective positive electrode layer _of, 12A 2, 12A ₃ and perform each collector at 12A _4. The same applies to the negative electrode unit 10B _u ''. That is, in the negative electrode unit 10B _u '', the negative electrode layers 11B ₁ , 11B ₂ , 11B ₃ and 11B ₄ are formed in the negative electrode current collecting layers 12B ₁ , 12B ₂ , 12B ₃ and 12B ₄ adjacent to each of the negative electrode layers. Each collects electricity.

With the above configuration, the connection between the current collector layer and the electrode terminals can be made more flexible. Further, as compared with the structure in which the current is collected by the current collecting layer provided in the connecting portion, the separator is easily interposed between the positive electrode and the negative electrode, and the manufacturing process is particularly easy to be facilitated.

In the present invention, the electrode assembly can be constructed by bending the electrodes. For example, 'the electrode units _10A u ~ 10A _u' negative polar body 100-100 'comprising an electrode has three or more electrode layers connecting portions 13A and 13B of the' and _10B u ~ 10B _{u '',} bent by zigzag This constitutes the electrode assembly. Thereby, the electrode layers 11A and 11B of the electrode units _{10A u} ~ _10A u _'' and _{10B u} ~ _10B u _'' constitute each electrode as the electrode assembly.

Here, "spin turn" refers to, for example, the following method (see FIG. 4 and the like).
-Bend the connecting portions 13A ₁ and 13B ₁ of the electrode unit along the longitudinal direction L in the direction f ₁ of the arrow.
· Next, the connecting portions 13A ₂ and 13B _2, along the longitudinal direction L bent in the direction _{f 2} of the arrows.
- Finally, the connecting portion 13A ₃ and 13B _3, bent in the direction _{f 3} of the arrows along the longitudinal direction L.

In the present invention, since the positive and negative electrodes including the electrode unit are first prepared and the electrode assembly is prepared using the positive and negative electrodes, a single electrode having only one electrode layer per side is used. Compared with the case where only the unit is used, the space of the secondary battery can be saved and the manufacturing process can be facilitated.

In one embodiment, in the positive electrode body, at least one of the electrodes includes a plurality of electrode units including two electrode layers and a connecting portion provided between the electrode layers.

In the exemplary embodiment shown in FIG. 7A, in the positive electrode unit 10A _u '', two positive electrode layers 11A including the positive electrode current collector 1A are connected via the positive electrode connecting portion 13A. The positive electrode unit 10A _u '''' also has a positive electrode current collecting layer 12A in close proximity to the positive electrode layer 11A. Here, the positive electrode current collector layer 12A is provided in the positive electrode connecting portion 13A. The negative electrode unit 10B _u '''' has a similar structure.

In the exemplary embodiment shown in FIG. 8, the positive and negative electrode bodies 100 ″ ″ include two positive electrode units 10A _u ″ and two negative electrode units 10B _u ″ ″. In the positive electrode body 100 ″, the positive electrode unit 10A _u ″ and the negative electrode unit 10B _u ″ are alternately superposed. In FIG. 8, the separator between the electrodes is omitted.

In the plan view of the positive electrode body 100 ″, the positive electrode connecting portion 13A is positioned at a position away from the central axis xx ″ of the positive electrode body 100 ″. Further, in the plan view of the positive and negative electrode body 100''', the negative electrode connecting portion 13B is located at a position away from the central axis xx'of the positive and negative electrode body 100''' and on the side opposite to the positive electrode connecting portion 13A. It is positioned.

'Respectively, each positive electrode unit 10A u' plurality of cathode units 10A u _'' has a structure for collecting current in the positive current collector layer 12A provided as the connecting portion 13A in the _''. Similarly, 'respectively, each negative electrode unit 10B u' more negative electrode units 10B u _'' has a structure for collecting current on the negative electrode collector layer 12B provided as a connecting portion 13B at the _''.

By bending the coupling portion 13A and 13B of the positive and negative electrode body 100 '''electrode units 10A _{u in'} '' and 10B _{u ''} '1 times, the electrode assembly is constructed. As a result, the electrode layers 11A and 11B of the electrode units 10A _u ″ and 10B _u ″'' constitute each electrode.

As described above, when the positive and negative electrode bodies have a plurality of positive and negative electrode units, the electrode assembly can be constructed by bending the connecting portion of each electrode unit only once, which makes the manufacturing process easier. Can be transformed into.

In the aspect of the positive electrode body described above, the electrode layer has a circular shape (see FIGS. 3A, 5A, 6A and 7A) and a quadrangular shape (see FIGS. 3B, 5B, 6B and 7B) in a plan view. , Or other irregular shapes.

In one embodiment, the electrode assembly 200 composed of the positive and negative electrode bodies 100 and 100'shown in FIGS. 4 and 5 is housed in the exterior body 300 together with the electrolyte (not shown) to form the secondary battery 400 (FIG. 4). 9).

The exterior body 300 has a positive electrode conductive portion 300A and a negative electrode conductive portion 300B that are separated from each other by an insulating portion 300I in a plan view of the secondary battery 400.

The positive electrode current collecting layer 12A (that is, the positive electrode connecting portion 13A) and the negative electrode current collecting layer 12B (that is, the negative electrode connecting portion 13B) in the electrode assembly 200 are in contact with the positive electrode conductive portion 300A and the negative electrode conductive portion 300B of the exterior body 300, respectively. ing.

A more detailed description will be given based on the cross-sectional view of the secondary battery 400 illustrated in FIGS. 10A and 10B. In the electrode assembly 200, the positive electrode 10A (that is, the positive electrode current collector 1A and the positive electrode material 2A) and the negative electrode 10B (that is, the negative electrode current collector 1B and the negative electrode material 2B) are alternately laminated via the separator 20. There is.

In a cross-sectional view of the secondary battery 400, the positive electrode layer formed by forming the positive electrode material 2A on the positive electrode current collector 1A and the negative electrode layer formed by forming the negative electrode material 2B on the negative electrode current collector 1B face each other. ing.

In one preferred embodiment, both the positive and negative electrodes include an electrode unit, and the connecting portion of the electrode unit is positioned to the side of the electrode of the opposite electrode in a cross-sectional view of the secondary battery. That is, when the positive electrode unit and the negative electrode unit are combined to form an electrode assembly with each other, the position of the connecting portion in one electrode unit is lateral to the electrode portion of the other electrode unit (particularly preferably). , The side opposite to the side where the connecting portion of the other electrode unit is provided) may be proximal. As a result, it becomes easy to construct the electrode assembly by the zigzag folding, and it becomes easy to provide the connecting portion as an output tab in the obtained electrode assembly.

Taking the electrode unit on the positive electrode side as an example, each positive electrode layer is electrically connected by a positive electrode connecting portion 13A, and the positive electrode connecting portion 13A is connected to the negative electrode 10B (that is, that is, in a cross-sectional view of the secondary battery 400). It is positioned on the side of the negative electrode layer). The "side" here can be regarded as a direction orthogonal to the electrode stacking direction of the electrode assembly in the cross-sectional view of the secondary battery. Further, the positive electrode connecting portion 13A is in contact with the positive electrode conductive portion 300A of the exterior body 300 (see FIG. 10A).

Similarly, in the electrode unit on the negative electrode side, each negative electrode layer is electrically connected by the negative electrode connecting portion 13B, and the negative electrode connecting portion 13B is connected to the positive electrode 10A (that is, the positive electrode) in a cross-sectional view of the secondary battery 400. It is positioned on the side of the layer). Further, the negative electrode connecting portion 13B is in contact with the negative electrode conductive portion 300B in the exterior body 300 (see FIG. 10B).

As described above, the positive electrode 10A collects current at the positive electrode current collecting layer 12A (that is, the positive electrode connecting portion 13A) adjacent to the positive electrode layer. Further, the negative electrode 10B collects electricity at the negative electrode current collecting layer 12B (that is, the negative electrode connecting portion 13B) close to the negative electrode layer.

In the secondary battery having the electrode assembly composed of the positive electrode body 100 ″ shown in FIG. 6, the positive electrode protruding portion is in contact with the positive electrode conductive portion in the exterior body, and the negative electrode protruding portion is the negative electrode conductive portion in the exterior body. Is in contact with. That is, the positive electrode collects electricity at the positive electrode current collecting layer provided in the positive electrode protruding portion close to the positive electrode layer. Further, the negative electrode collects electricity from the negative electrode current collecting layer provided in the negative electrode protruding portion close to the negative electrode layer.

The electrode assembly 200 composed of the positive and negative electrode bodies 100 is preferably configured by sequentially folding an electrode unit having a plurality of connecting portions. Therefore, in the cross-sectional view of the secondary battery 400, the positive electrode connecting portions 13A ₁ and 13A ₃ and the positive electrode connecting portion 13A ₂ are positioned on different sides of the negative electrode 10B (see FIG. 10A). Further, the negative electrode connecting portions 13B ₁ and 13B ₃ and the negative electrode connecting portion 13B ₂ are positioned on different sides of the positive electrode 10A (see FIG. 10B).

The electrode assembly 200 made of the positive and negative electrode bodies 100'is formed by folding an electrode unit having a single connecting portion in a zigzag manner. Therefore, in the cross-sectional view of the secondary battery 400, the positive electrode connecting portions 13A ₁ and 13A ₃ and the positive electrode connecting portion 13A ₂ extend so as to be positioned on different sides of the negative electrode 10B (see FIG. 10A). ). Further, the negative electrode connecting portions 13B ₁ and 13B ₃ and the negative electrode connecting portion 13B ₂ extend so as to be positioned on different sides of the positive electrode 10A (see FIG. 10B).

In one embodiment, adjacent current collector layers are adhered to each other in a cross-sectional view of the secondary battery. In the illustrated embodiment, in the cross-sectional view of the secondary battery 400, adjacent positive electrode current collector layers (that is, positive electrode connecting portions 13A ₁ and 13A ₃ ) are adhered to each other (see FIG. 11A). Further, adjacent negative electrode current collector layers (that is, negative electrode connecting portions 13B ₁ and 13B ₃ ) are adhered to each other (see FIG. 11B). As shown, adjacent current collector layers are individually folded and adhered to each other. In a broad sense, the term "adhesion" used in connection with the current collector layer / connecting portion means that the target current collecting layer / connecting portion is electrically connected to each other. , For example, various specific aspects such as welding and bonding.

By adhering adjacent current collector layers to each other in a cross-sectional view of the secondary battery, electrical connection with the exterior body becomes easier. It is preferable that at least two of the adjacent current collector layers are adhered to each other, for example, all the adjacent current collector layers are adhered to each other.

In one embodiment, in a cross-sectional view of the secondary battery 400, the exterior body 300'has a positive electrode conductive portion 300A'and a negative electrode conductive portion 300B' separated from each other by an insulating portion 300I'(FIG. 12 and FIG. 12 and See FIG. 13).

The positive electrode connecting portion 13A and the negative electrode connecting portion 13B in the electrode assembly 200 are in contact with the positive electrode conductive portion 300A'and the negative electrode conductive portion 300B' in the exterior body 300', respectively (see FIG. 13). When the secondary battery 400 according to the present embodiment is viewed in a plan view, the positive electrode connecting portion 13A and the negative electrode connecting portion 13B are separated from the exterior body 300'(see FIG. 12).

Each positive electrode layer is electrically connected by the positive electrode connecting portion 13A, and the positive electrode connecting portion 13A is in contact with the positive electrode conductive portion 300A of the exterior body 300 (see FIG. 13A). Further, each negative electrode layer is electrically connected at the negative electrode connecting portion 13B, and the negative electrode connecting portion 13B is in contact with the negative electrode conductive portion 300B (see FIG. 13B).

In one embodiment, the electrode assembly 200'consisting of the positive and negative electrode bodies 100'''shown in FIG. 8 is housed in the exterior body 300 together with the electrolyte (not shown) to form the secondary battery 400 (see FIG. 14). ).

The positive electrode current collecting layer 12A (that is, the positive electrode connecting portion 13A) and the negative electrode current collecting layer 12B (that is, the negative electrode connecting portion 13B) in the electrode assembly 200'are attached to the positive electrode conductive portion 300A and the negative electrode conductive portion 300B in the exterior body 300, respectively. I'm in contact.

A more detailed description will be given based on the cross-sectional view of the secondary battery 400 illustrated in FIGS. 15A and 15B. In the electrode assembly 200', the positive electrode 10A (that is, the positive electrode current collector 1A and the positive electrode material 2A) and the negative electrode 10B (that is, the negative electrode current collector 1B and the negative electrode material 2B) are alternately laminated via the separator 20. ing.

In a cross-sectional view of the secondary battery 400, the positive electrode layer in which the positive electrode material 2A is formed on the positive electrode current collector 1A and the negative electrode layer in which the negative electrode material 2B is formed on the negative electrode current collector 1B face each other.

Here, the two positive electrode layers in each positive electrode unit are electrically connected to each other by the positive electrode connecting portion 13A, and the positive electrode connecting portion 13A is the negative electrode 10B (that is, the negative electrode layer) in the cross-sectional view of the secondary battery 400. It is positioned on the side of. Further, the positive electrode connecting portion 13A is in contact with the positive electrode conductive portion 300A of the exterior body 300 (see FIG. 15A).

Similarly, the two negative electrode layers in each negative electrode unit are electrically connected to each other by the negative electrode connecting portion 13B, and the negative electrode connecting portion 13B is the positive electrode 10A (that is, the positive electrode layer) in the cross-sectional view of the secondary battery 400. It is positioned on the side of. Further, the negative electrode connecting portion 13B is in contact with the negative electrode conductive portion 300B in the exterior body 300 (see FIG. 15B).

In the present embodiment, adjacent current collector layers are in contact with each other in a cross-sectional view of the secondary battery. In the illustrated embodiment, in a cross-sectional view of the secondary battery 400, adjacent positive electrode current collector layers (that is, positive electrode connecting portions 13A ₁ and 13A ₂ ) are in contact with each other (see FIG. 15A). Further, adjacent negative electrode current collector layers (that is, negative electrode connecting portions 13B ₁ and 13B ₂ ) are in contact with each other (see FIG. 15B). Here, it is preferable that the adjacent current collector layers are adhered to each other.

As described above, in the positive electrode 10A, current collection is performed by the positive electrode current collecting layer 12A (that is, the positive electrode connecting portion 13A) adjacent to the positive electrode layer. Further, in the negative electrode 10B, current collection is performed by the negative electrode current collecting layer 12B (that is, the negative electrode connecting portion 13B) close to the negative electrode layer.

The electrode assembly 200'consisting of the positive and negative electrode bodies 100'''is formed by bending the connecting portion of the electrode unit once. Therefore, in the cross-sectional view of the secondary battery 400, the positive electrode connecting portions 13A ₁ and 13A ₂ are positioned on the same side of the negative electrode 10B (see FIG. 15A). Further, the negative electrode connecting portions 13B ₁ and 13B ₂ are respectively positioned on the same side of the positive electrode 10A (see FIG. 15B).

[Material of each component of the secondary battery according to the present invention, etc.]
The positive electrode is composed of at least a positive electrode material and a positive electrode current collector. The positive electrode material contains a positive electrode active material as an electrode active material. Further, the negative electrode is composed of at least a negative electrode material and a negative electrode current collector. The negative electrode material contains a negative electrode active material as an electrode active material.

The electrode active materials contained in the positive electrode material and the negative electrode material, 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 mainly responsible for charge / discharge, that is, the battery reaction. It is a substance.

More specifically, ions are brought to the electrolyte due to the "positive electrode active material" and the "negative electrode active material", and such ions move between the positive electrode and the negative electrode to transfer electrons and fill the electrolyte. Discharge is done.

It is particularly preferable that the positive electrode material and the negative electrode material contain an electrode active material capable of occluding and releasing lithium ions. That is, it is preferable to use 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 and discharging, the secondary battery of the present invention corresponds to a so-called "lithium ion battery", and a positive electrode layer containing a positive electrode material and a negative electrode layer containing a negative electrode material can occlude and release lithium ions. Is.

The positive electrode active material is composed of particles, for example, and it is preferable that the positive electrode material contains a binder (also referred to as a "binding material") for more sufficient contact between particles and shape retention. Further, a conductive auxiliary agent may be contained in the positive electrode material in order to facilitate the transfer of electrons that promote the battery reaction.

Similarly, where the negative electrode active material is composed of, for example, granules, it preferably contains a binder for better contact between the particles and shape retention, and is conductive to facilitate the transfer of electrons that drive the battery reaction. Auxiliary agent may be contained in the negative electrode material.

As described above, the positive electrode material and the negative electrode material can also be referred to as "positive electrode mixture" and "negative electrode mixture", respectively, because of the form in which a plurality of components are contained.

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 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 of the secondary battery according to the present embodiment, such a lithium transition metal composite oxide is preferably contained as the positive electrode active material. For example, the positive electrode active material is 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. In a more preferred embodiment, the positive electrode active material contained in the positive electrode material is lithium cobalt oxide.

The binder that can be contained in the positive electrode material is not particularly limited, but is not particularly limited, such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and polytetrafluoroethylene. At least one species selected from the group consisting of can be mentioned. The conductive auxiliary agent that can be contained in the positive electrode material 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-grown carbon. At least one selected from carbon fibers such as fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. In a more preferred embodiment, the binder of the positive electrode material is polyvinylidene fluoride, and in another more preferred embodiment, the conductive auxiliary agent of the positive electrode material is carbon black. In a more preferred embodiment, the binder and conductive aid of the positive electrode material are a combination of polyvinylidene fluoride and 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 is preferably, for example, various carbon materials, oxides, lithium alloys, and the like.

Examples of various carbon materials for the negative electrode active material include graphite (natural graphite, artificial graphite), hard carbon, soft carbon, and diamond-like carbon. 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 is a binary, ternary or higher alloy of a metal such as La and lithium. Such oxides are preferably amorphous as their structural form. This is because deterioration due to non-uniformity such as grain boundaries or defects is less likely to occur. In a more preferred embodiment, the negative electrode active material is artificial graphite.

The binder that can be contained in the negative electrode material is not particularly limited, but at least one selected from the group consisting of styrene butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resin and polyamide-imide resin may be used. Can be mentioned. In a more preferred embodiment, the binder contained in the negative electrode material is styrene-butadiene rubber. The conductive auxiliary agent that can be contained in the negative electrode material 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-grown carbon. At least one selected from carbon fibers such as fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. The negative electrode material may contain a component derived from a thickener component (for example, carboxylmethyl cellulose) used at the time of manufacturing the battery.

In a more preferred embodiment, the negative electrode active material and the binder in the negative electrode material 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 by the active material due to the battery reaction. Such a current collector may be a sheet-like metal member and may have a perforated or perforated form. For example, the current collector may be metal leaf, punching metal, mesh or 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 is, 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 is, for example, a copper foil.

The separator is a member provided from the viewpoint of preventing a short circuit due to contact between the positive and negative electrodes and retaining the 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 secondary battery according to the present invention, an electrode assembly including a positive electrode, a negative electrode and a separator is enclosed in an outer body together with an electrolyte. The electrolyte assists the movement of metal ions released from the electrodes (positive electrode / negative electrode). The electrolyte may be a "non-aqueous" electrolyte such as an organic electrolyte and an organic solvent, or it may be a "water-based" electrolyte containing water. The secondary battery according to 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 the electrolyte. The electrolyte may have a form such as liquid or gel (note that the "liquid" non-aqueous electrolyte is also referred to as "non-aqueous electrolyte solution" in the present specification).

As a specific non-aqueous electrolyte solvent, one containing at least carbonate is preferable. 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). 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 a specific solute of the non-aqueous electrolyte, for example, Li salts such as LiPF ₆ and LiBF ₄ are preferable.

The exterior body may be a hard case. The hard case may consist of two members configured in combination with each other. That is, the exterior body has, for example, a two-part configuration of a first exterior body and a second exterior body. One of the exterior bodies having a two-part structure may form a positive electrode conductive portion, and the other may form a negative electrode conductive portion. For example, when the exterior body is composed of a positive electrode conductive portion and a negative electrode conductive portion, the positive electrode conductive portion and the negative electrode conductive portion are sealed after accommodating the electrode assembly, the electrolyte, and optionally the electrode terminals. The sealing method is not particularly limited, and examples thereof include a laser irradiation method.

As the material for forming the positive electrode conductive part and the negative electrode conductive part of the exterior body, any material that can form a hard case type exterior body can be used in the field of the secondary battery. Such a material may be a conductive material in which electron transfer can be achieved, or an insulating material in which electron transfer cannot be achieved. The material of the exterior body is preferably a conductive material from the viewpoint of taking out the electrodes.

Examples of the conductive material include a metal material selected from the group consisting of silver, gold, copper, iron, tin, platinum, aluminum, nickel, stainless steel and the like. Examples of the insulating material include insulating polymer materials selected from the group consisting of polyester (eg, polyethylene terephthalate), polyimide, polyamide, polyamide-imide, and polyolefin (eg, polyethylene, and polypropylene).

From the viewpoint of conductivity and rigidity described above, it is preferable that both the positive electrode conductive portion and the negative electrode conductive portion are made of stainless steel. As defined in "JIS G0203 Steel Terms", stainless steel is an alloy steel containing chromium or chromium and nickel, and generally has a chromium content of about 10.5% or more of the total. Refers to steel. Examples of such stainless steels include stainless steels selected from the group consisting of martensite-based stainless steels, ferrite-based stainless steels, austenitic stainless steels, austenitic-ferrite-based stainless steels, and precipitation-hardened stainless steels.

The dimensions of the positive electrode conductive portion and the negative electrode conductive portion of the exterior body are mainly determined according to the dimensions of the electrode assembly. For example, when the electrode assembly is housed, the movement of the electrode assembly inside the exterior body is prevented. It is preferable to have dimensions. By preventing the electrode assembly from moving, damage to the electrode assembly due to impact or the like can be prevented, and the safety of the secondary battery can be improved.

The exterior body may be a flexible case such as a pouch made of a laminated film. The laminated film has a structure in which at least a metal layer (for example, aluminum) and an adhesive layer (for example, polypropylene and polyethylene) are laminated, and an additional protective layer (for example, nylon and polyamide) is laminated. May be configured.

The secondary battery may be provided with an electrode terminal. That is, the secondary battery may be provided with a terminal for electrically connecting to the outside. Such electrode terminals may be provided on at least one surface of the exterior body. For example, positive and negative electrode terminals may be provided on the same surface of the exterior body so as to be separated from each other. Alternatively, positive and negative electrode terminals may be provided on different surfaces of the exterior body.

It is preferable to use a material having a high conductivity for the electrode terminal. The material of the electrode terminal is not particularly limited, and at least one selected from the group consisting of silver, gold, copper, iron, tin, platinum, aluminum, nickel, and stainless steel can be mentioned.

[Method for manufacturing secondary battery according to the present invention]
The secondary battery of the present invention can be manufactured by a method including at least a manufacturing process of an electrode unit, a manufacturing process of a positive electrode body, and a manufacturing process of an electrode assembly. The method for manufacturing a secondary battery of the present invention finally includes a sealing step. Hereinafter, each step will be briefly described, but the above-mentioned description of the secondary battery may be referred to as appropriate.

(Manufacturing process of electrode unit)
In this step, an electrode unit is obtained by cutting out from an electrode precursor provided with an electrode material on a current collector.

For the electrode precursor, the electrode material paste is applied to a metal sheet material used as a current collector (for example, the positive electrode current collector is an aluminum foil and the negative electrode current collector is a copper foil) and rolled by a roll press machine. As a result, an electrode precursor is obtained.

The area to be applied is determined so that the desired electrode layer and current collector layer can be obtained. For example, in the case of manufacturing the electrode unit of FIG. 3A, the electrode material is provided with a certain gap so as to obtain a connecting portion as a current collecting layer having a desired length along any one direction of the metal sheet material. Apply the paste in a substantially circular shape.

Next, the electrode unit is obtained by cutting out the region to which the electrode material paste is applied and the region to which the electrode material paste is not applied so as to correspond to the connecting portion of the electrode unit. For example, in the case of manufacturing the electrode unit of FIG. 3A, a desired connection is made along the outer edge of the region where the electrode material paste is applied in a substantially circular shape, and the region where the electrode material paste is not applied provided between the regions. Cut out so that it has the shape of the part.

The cutting out is just an example, but it may be a so-called "punching operation".

(Manufacturing process of positive and negative electrodes)
In this step, the positive electrode and the negative electrode are superposed to obtain a positive electrode body.

As described above, in the positive electrode body, the positive electrode and the negative electrode are overlapped with each other via the separator. When the positive electrode body of FIG. 4 is manufactured, the positive electrode layer and the negative electrode layer in each electrode unit are superposed so as to be alternately overlapped with each other via a separator.

The separator may be inserted between the positive electrode layer and the negative electrode layer. The separator may be a sheet cut and laminated, or may be laminated in a zigzag to cut the excess. Alternatively, the separator may individually package the electrode or the electrode unit.

In this step, as described above, it is preferable that the electrode layers that are overlapped with each other via the separator in the positive and negative electrodes are adhered from the viewpoint of further improving the handleability of the electrodes. Adhesion can be performed by a method using an adhesive separator as a separator, a method of applying an adhesive binder on the electrode layer, and / or a method of thermocompression bonding.

(Manufacturing process of electrode assembly)
In this step, for example, as shown in FIG. 4, the connecting portions 13A and 13B of the electrode units 10A _u and 10B _u in the positive and negative polar body 100, by folding the serpentine, the electrode assembly is constructed. The number of bends may be appropriately determined according to the number of electrode layers contained in one electrode unit.

After the positive and negative electrodes are bent to obtain an electrode assembly, it is usually preferable to perform adhesion so that the state is maintained. Adhesion may be performed by adhering the electrode layers that come into contact with each other via the separator for the first time by bending. As the bonding method, the same method as the bonding method that may be performed in the manufacturing process of the positive electrode body can be used.

Further, if desired, adjacent current collector layers (for example, positive electrode connecting portions 13A ₁ and 13A ₂ in FIG. 11A) are adhered in a cross-sectional view of the electrode assembly. Adhesion of adjacent current collector layers may be performed by, for example, heat welding, laser welding and ultrasonic welding, and a conductive adhesive.

(Encapsulation process)
A secondary battery can be obtained by encapsulating the electrode assembly together with the electrolyte in the exterior body.

The secondary battery according to 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, smartphones, laptop computers and digital cameras, activity meters, arm computers, electronic papers, etc.) in which electric and electronic devices are used. , Wearable devices, RFID tags, card-type electronic money, smart watches, etc. in the electric / electronic equipment field or mobile equipment field), home / small industrial applications (for example, power tools, golf carts, home / nursing / industrial use) Robots), large industrial applications (eg forklifts, elevators, bay port cranes), transportation systems (eg hybrids, electric vehicles, buses, trains, electrically assisted bicycles, electric motorcycles, etc.), electricity System applications (for example, various power generation, road conditioners, smart grids, general household installation type power storage systems, etc.), medical applications (medical equipment fields such as earphone hearing aids), pharmaceutical applications (fields such as dose management systems), and , IoT field, space / deep sea applications (for example, fields such as space explorers and submersible research vessels).

The secondary battery according to the present invention has a lower resistance while maintaining a high battery capacity. Therefore, the secondary battery according to the present invention can be particularly preferably used for a wearable device that requires high energy density and high-speed charge / discharge characteristics. Here, the wearable device refers to a device that can be used while being worn in the form of clothes or a wristwatch, such as a head-mounted display or a smart watch.

1: Current collector 1A: Positive electrode current collector 1B: Negative electrode current collector 2: Electrode material 2A: Positive electrode material 2B: Negative electrode material 10: Electrode 10A: Positive electrode 10B: Negative electrode 11: Electrode layer 11A: Positive electrode layer 11B: Negative electrode layer 12: Current collecting layer 12A: Positive electrode current collecting layer 12B: Negative electrode current collecting layer 13: Connecting part 13A: Positive electrode connecting part 13B: Negative electrode connecting part 14: Protruding part 14A: Positive electrode protruding part 14B: Negative electrode protruding part 10 _U : Electrode unit 10A _U : Positive electrode unit 10B _U : Negative electrode unit 20: Separator 100: Positive and negative electrode body 200: Electrode assembly 300: Exterior body 300A: Positive electrode conductive part 300B: Negative electrode conductive part 300I: Insulation part 400: Secondary battery

Claims (12)

1. 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.
   The positive electrode and the negative electrode have an electrode layer in which an electrode material is formed on the current collector, and a current collector layer in which the current collector is exposed.
   The electrode of at least one of the positive electrode and the negative electrode includes a plurality of the electrode layers facing the other electrode and an electrode unit including a connecting portion for electrically connecting the plurality of electrode layers, and the connecting portion includes the connecting portion. It is positioned on the side of the other electrode in the cross-sectional view of the secondary battery.
   A secondary battery in which the positive electrode and the negative electrode collect current in the current collecting layer close to the electrode layer.
2. The secondary battery according to claim 1, wherein in the electrode unit, each part of the connecting portion located between the electrode layers adjacent to each other serves as an output tab.
3. The secondary battery according to claim 1 or 2, wherein the connecting portions are linearly aligned or extended in a plan view in which the electrode unit is developed.
4. Claim 1 in which both the positive electrode and the negative electrode include the electrode unit, and the connecting portion of the electrode unit is positioned on the side of the electrode having a different electrode in a cross-sectional view of the secondary battery. The secondary battery according to any one of 3 to 3.
5. One of claims 1 to 4, wherein at least one electrode of the positive electrode and the negative electrode includes the electrode unit including three or more electrode layers and a plurality of the connecting portions provided between the electrode layers. The described secondary battery.
6. A claim comprising the electrode unit comprising the connecting portion in which at least one of the positive electrode and the negative electrode is provided in a single shape so as to straddle each of the three or more electrode layers and the electrode layers. Item 4. The secondary battery according to any one of Items 1 to 4.
7. The invention according to any one of claims 1 to 4, wherein at least one electrode of the positive electrode and the negative electrode includes a plurality of the electrode units including the two electrode layers and the connecting portion provided between the electrode layers. Secondary battery.
8. The secondary battery according to any one of claims 1 to 7, wherein the adjacent current collector layers are adhered to each other in a cross-sectional view of the secondary battery.
9. The secondary battery according to any one of claims 1 to 8, wherein the connecting portion comprises the current collecting layer.
10. The secondary battery according to claim 9, wherein the electrodes collect current at the connecting portion.
11. The secondary battery according to any one of claims 3 to 9, which is subordinate to claim 1, wherein the electrode collects current at a portion other than the connecting portion.
12. A wearable device using the secondary battery according to any one of claims 1 to 11.

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