JP2017091947A - Electrode structure for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure for a secondary battery in which a favorable conductive path can be formed without bias between a current collector and an active material in an electrode mixture held by the current collector.SOLUTION: An electrode structure 10A is a plate-like structure as a whole, and includes one or plural current collectors (15A) which are formed so that at least some of them extend in the thickness direction of the plate-like structure from one wider flat surface of the plate-like structure to the other wide flat surface, and an electrode mixture layer (16A) in contact with the current collectors. The current collectors and the electrode mixture layer co-exist while a predetermined regularity is maintained in the entire region from one end to the other end in one direction orthogonal to the thickness direction of the plate-like structure.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrode structure for a secondary battery that can be used as an electrode provided in a secondary battery such as a nickel metal hydride battery or a lithium secondary battery.

  Secondary batteries are used as a power source for a wide range of applications. Particularly recently, nickel-metal hydride batteries (which are terms in a broad sense and include nickel metal hydride batteries (Ni-MH) in a narrow sense; the same shall apply hereinafter), lithium secondary batteries (so-called lithium ion secondary batteries, Secondary batteries having a relatively high capacity and excellent rapid charge / discharge performance (high rate characteristics), such as lithium polymer secondary batteries, etc.) are widely used as power sources for driving vehicles such as automobiles. It is used. For example, relatively large nickel metal hydride batteries and lithium secondary batteries are widely used as driving power sources for hybrid vehicles and the like.

As described above, a secondary battery used as a driving power source is required to have performance (high rate characteristics) that enables rapid charge / discharge, and improvements for that purpose can be made from various viewpoints regarding the configuration of the secondary battery. It has been broken. One approach to this is to examine and improve the electrode configuration and structure.
In particular, in order to realize an increase in battery capacity and a more rapid ion and electron transfer between electrodes, active researches are being conducted on improving the composition and shape of the active material for each of the positive and negative electrodes. In recent years, many attempts have been made to develop high-performance active materials using inorganic and organic hybrid materials (so-called inorganic / organic hybrid materials).
For example, Patent Document 1 discloses a secondary battery including a zinc negative electrode formed by applying a zinc mixture containing a zinc-containing compound as a negative electrode active material to a current collector such as a nickel mesh.

JP 2014-026951 A

By the way, in order to improve the high-rate characteristics and the like, a good electron conduction path or ion conduction path between the active material in the positive electrode mixture or the negative electrode mixture held in the current collector and the current collector ( Hereinafter, these are collectively referred to as “conductive paths”). In particular, when using a positive electrode mixture or a negative electrode mixture containing an inorganic / organic hybrid material in which nano-sized minute active material particles and an organic material (typically an organic electrolyte) are present in a highly dispersed state, In order to realize an improvement in high rate characteristics and the like, it is important to build a good conductive path between the active material in the composite material and the current collector as well as stably holding the composite material on the current collector.
Therefore, the present invention has been created to solve such problems, and forms a good conductive path without bias between the current collector and the active material in the electrode mixture held by the current collector. The object is to provide a possible electrode structure.

The electrode structure disclosed here is an electrode structure used for a positive electrode or a negative electrode of a secondary battery. The electrode structure is a plate-like (in other words, sheet-like) structure as a whole.
The plate-like structure is a current collector that constitutes at least a part of the plate-like structure, and at least a part of the plate-like structure extends from one wide plane of the plate-like structure in the thickness direction of the plate-like structure. It has one or a plurality of current collectors formed so as to extend to the other wide flat surface, and an electrode mixture layer held by the current collector.
The current collector and the electrode mixture layer are mixed while maintaining a predetermined regularity in the entire region from one end to the other end in one direction orthogonal to the thickness direction of the plate-like structure. It is characterized by that.

In the electrode structure having such a configuration, the current collector and the electrode mixture layer coexist while maintaining a predetermined regularity throughout the plate-like (also referred to as thin plate or sheet) electrode structure. In other words, the electrode structure that is plate-like when viewed macroscopically in this configuration is that the current collector and the electrode mixture layer are obtained by looking at the constituent elements along one direction orthogonal to the thickness direction. It is composed of a mixed structure with regularity.
Accordingly, in the electrode structure of this configuration, for example, a plate-like electrode structure having the same volume, and a similar sheet-like assembly is formed on one or both of the surfaces of the electrode mixture layer formed in one sheet form. Compared with a conventional plate-like electrode structure in which an electric body is disposed, the conductive path between the current collector and the active material in the electrode mixture layer held by the current collector is reduced as a whole of the electrode structure. Can be increased without bias.
Therefore, according to the present invention, it is possible to provide an electrode structure that contributes to improving battery performance such as high rate characteristics.

Moreover, in one preferable aspect of the electrode structure disclosed herein, the one end portion in the one direction perpendicular to the thickness direction of the plate-like structure of the current collector and the electrode mixture layer is the other end portion. It is characterized in that it is realized that one sheet-like current collector having a bellows shape (corrugated shape) is arranged to be mixed while maintaining a predetermined regularity in all the regions up to .
In another preferred embodiment of the electrode structure disclosed herein, the current collector and the electrode mixture layer are arranged from one end in one direction perpendicular to the thickness direction of the plate-like structure to the other. It is realized by a laminated structure in which sheet-like current collectors and electrode composites are alternately laminated in the same direction to be mixed while maintaining a predetermined regularity in the entire region up to the end. It is characterized by.

In another preferred embodiment of the electrode structure disclosed herein, the current collector and the electrode mixture layer are arranged from one end in one direction perpendicular to the thickness direction of the plate-like structure to the other. It is mixed in while maintaining a predetermined regularity in the entire region up to the end, and the current collector formed in a spiral shape as viewed from the wide plane and the spiral groove portion corresponding to the spiral current collector. It is realized by the configuration with the electrode mixture arranged.
According to these structures, the battery performance such as the high rate characteristic can be preferably improved.

It is the partially broken perspective view which shows typically an example of the secondary battery (nickel metal hydride battery) equipped with the electrode structure disclosed here as a positive electrode or a negative electrode. It is a perspective view showing typically the whole structure of the electrode structure concerning a 1st embodiment. It is a perspective view which shows typically the whole structure of the electrode structure which concerns on 2nd Embodiment. It is a perspective view which shows typically the whole structure of the electrode structure which concerns on 3rd Embodiment.

Hereinafter, some preferred embodiments of the electrode structure disclosed herein will be described with reference to the drawings.
Matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, the general configuration and manufacturing process of the entire secondary battery not characterizing the present invention) It can be grasped as a design matter of those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. In addition, dimensional relationships (length, width, thickness, etc.) in the following drawings are deformed for ease of explanation, and do not reflect actual dimensional relationships.

In this specification, the “secondary battery” refers to a general power storage device that can be repeatedly charged and discharged, and is a term that includes power storage elements such as a so-called storage battery and an electric double layer capacitor.
In addition, the “electrode mixture” refers to a composition (a mixture) containing an active material of any one of the positive and negative electrodes, and the contents of the active material and other components (various additives) constituting the mixture are as follows: Depending on the type of secondary battery, such as a nickel metal hydride battery or a lithium secondary battery.
Therefore, an electrode mixture layer (specifically, a positive electrode mixture layer or a negative electrode mixture layer) is a layer mainly composed of an active material formed by applying the electrode mixture to a current collector. (Also referred to as an active material layer), and the composition of the electrode mixture before being applied to the current collector and the composition of the composition constituting the electrode mixture layer (active material layer) are not necessarily the same is not. For example, when an organic solvent is contained in the electrode mixture, the organic solvent is usually evaporated and lost during the formation of the electrode mixture layer. A layer formed by applying to the body can be referred to as an electrode mixture layer.

First, a box-shaped nickel-metal hydride battery will be briefly described as an example of a suitable secondary battery in which the electrode structure disclosed herein can be used as a positive electrode (or a negative electrode) with reference to FIG.
As shown in FIG. 1, the nickel metal hydride battery 100 according to this embodiment includes a battery case 40 including a lid 42. In the case 40, the positive electrode 10, the negative electrode 20, and the separator 30 which comprise the electrode body of the nickel metal hydride battery 100 which concerns on this embodiment are accommodated.
The positive electrode 10 is composed of a plurality of thin rectangular plate-like (sheet-like) electrode structures, which are electrically connected to the positive electrode terminal 14 via the positive electrode current collecting tab 12. On the other hand, the negative electrode 20 has the same shape as the positive electrode side, and is composed of a plurality of thin rectangular plate-shaped (sheet-shaped) electrode structures, which are connected to the case via a negative-electrode current collecting member (not shown). 40 is connected to a negative electrode terminal (not shown) provided on the bottom surface. Further, a spacer 60 and a gasket 50 provided around the spacer 60 are mounted on the inner side of the case 40 than the lid body 42, and the sealed state inside the case 40 is maintained.
The spacer 60 is formed with a gas discharge valve structure for discharging the internal gas to the outside of the case when the gas pressure inside the battery 100 (inside the case 40) becomes abnormally high. However, since it may be the same as that attached to the conventional nickel metal hydride battery and is not a structure that characterizes the present invention, further detailed description is omitted. Further, the materials and shapes of the constituent parts (positive and negative electrodes, separators, cases, etc.) of the nickel-metal hydride battery 100 are the same as those in the prior art except for the part to which the electrode structure 10A disclosed herein is applied. Since it may be the same as a nickel metal hydride battery and does not particularly characterize the present invention, further detailed description is omitted.

Next, the electrode structure 10A according to the first embodiment will be described in detail with reference to FIG. An electrode structure 10A according to the present embodiment is a structure constituting the positive electrode 10 in the nickel metal hydride battery 100 shown in FIG.
As shown in FIG. 2, the electrode structure 10 </ b> A according to this embodiment constituting the positive electrode 10 has a rectangular plate shape (sheet shape) corresponding to the shape of the battery case 40 as a whole. In the drawings, the size, shape, etc. (especially thickness) are deformed for explanation.
As shown in the figure, the electrode structure 10A according to the present embodiment is a rectangular sheet-shaped current collector as a skeleton, and has a predetermined shape in the long side direction so as to have a bellows (corrugated plate) shape. A current collector 15A having a shape that is alternately bent at intervals (hereinafter, referred to as a “bellows-type current collector 15A”) is provided.

Specifically, the bellows-type current collector 15A is disposed along the long side direction of the rectangular plate-like electrode structure 10A, and one end portion thereof is in the long side direction of the wide plane of the electrode structure 10A. The other end surface of the other side surface reaches the other end surface in the long side direction. Further, as shown in FIG. 2, the bent top end portion 17A on one surface side of the bent corrugated plate (zigzag) structure is arranged on one wide plane, and the bent top end portion 17B on the other surface side is a plate. The electrode structure 10A extends in the thickness direction and reaches the other wide plane.
The electrode mixture layer (here, positive electrode mixture layer) 16A is disposed on the surface of the bellows type current collector 15A. Specifically, an electrode mixture layer 16A is formed by filling a recessed portion formed by a bent corrugated plate (zigzag) structure with an electrode mixture. The bellows type current collector 15A and the electrode mixture layer 16A filled on both sides thereof form the rectangular plate-like electrode structure 10A.

As described above, in the rectangular plate-like electrode structure 10A according to the present embodiment, the bellows-type current collector 15A and the electrode mixture layer 16A disposed therearound are orthogonal to the thickness direction of the plate-like electrode structure 10A. In all the regions from one end to the other end in one direction (here, the long side direction of the wide plane), they are mixed while maintaining a predetermined regularity.
Thereby, according to the electrode structure 10A according to the present embodiment, the current between the current collector 15A and the active material in the electrode mixture layer 16A held by the current collector is not biased over the entire electrode structure. The conductive path can be increased.

The configuration shown in FIG. 2 is merely an example, and the shape of the current collector 15A extends from one wide plane of the plate-like structure 10A to the thickness direction of the plate-like structure to reach the other wide plane. In addition, the current collector and the electrode mixture layer maintain predetermined regularity in the entire region from one end to the other end in one direction orthogonal to the thickness direction. It is only necessary to be able to form a mixed state and is not particularly limited to the form shown in FIG. For example, in the form shown in FIG. 2, the bent top end portions 17A and 17B have a sharp pointed shape, but may be a top end portion formed of a gentle arc (R portion).
Further, the surface structure of the current collector 15A is not particularly limited, and may be a completely flat surface structure, but having an appropriate uneven structure from the viewpoint of increasing the contact area with the electrode mixture layer 16A. preferable. It may be porous, or may be punched to form small holes regularly. The angle of bending for forming the corrugated plate shape is not particularly limited. Typically, it is 60 degrees or more and 120 degrees or less. For example, about 90 ° ± 15 ° is preferable.

The size of the current collector 15A is not particularly limited because it may vary depending on the size and shape of the target secondary battery, but from the viewpoint of current collection efficiency, the thickness is, for example, about 10 μm to 50 μm. Is preferred.
Note that the shape of the current collector 15A (the size of the long side and the short side in a flat sheet state before being bent in a zigzag shape to obtain a corrugated plate shape) may vary depending on the plate shape of the electrode structure. In consideration of ion conductivity in the thickness direction of the entire electrode structure 10A, the size in the thickness direction is suitably 0.5 mm or less.

The means for holding the shape of the electrode structure 10A composed of the current collector 15A and the electrode mixture layer 16A is not particularly limited. For example, the electrode mixture disposed (filled) in the bellows type current collector 15A An appropriate amount of a binder (binder) may be included so that the electrode mixture layer 16A also has a function as an adhesive layer that maintains the shape of the electrode structure 10A with the current collector 15A. Good.
Although not shown, the electrode structure 10A may be restrained by some restraining member in order to achieve a high level of structural stabilization of the electrode structure 10A itself. For example, a tape (or string) -like restraining member can be employed.

The metal composition of current collector 15A that forms the skeleton of electrode structure 10A according to the present embodiment is not particularly limited as long as a conductive path with electrode mixture layer 16A can be constructed. It can be formed from various metals (or alloys) used for the positive and negative electrodes of this type of secondary battery. For example, a metal used for a positive electrode plate of a general nickel metal hydride battery, typically nickel or an alloy mainly composed of nickel can be used. A porous metal member (for example, a punching metal member used for an electrode plate of a conventional nickel metal hydride battery) may be used.
Further, the current collector 15A to be used may be magnetized. The bellows type current collector 15A may be magnetized after the construction of the electrode structure 10A. By being magnetized, the stability of the laminated structure itself can be further improved.
Alternatively, as shown in FIG. 2, the electrode structure 10A may be provided with a guide member (preferably a plate-shaped guide member) 19 preferably along a wide plane. By attaching the guide member 19, the structural stability can be improved. Furthermore, when the guide member 19 is made of a conductive member that can collect current, it can function as a current collector (collector) for the electrode.

On the other hand, the configuration of the electrode mixture layer 16A is not particularly limited, and any of various positive and negative electrodes of a type required depending on the type of the target secondary battery such as a nickel metal hydride battery or a lithium secondary battery. An active material (here, a positive electrode active material) and various additives (subcomponents) can be used.
For example, in the case of a positive electrode active material for a nickel metal hydride battery, an active material in which at least one nickel compound selected from nickel hydroxide, nickel oxyhydroxide, and derivatives thereof is included in the electrode mixture layer (positive electrode mixture layer) 16A. It can be a substance component.
In the active material composed of these nickel compounds, a part of nickel element may be substituted with other metal elements (cobalt, aluminum, zinc, manganese, tungsten, titanium, niobium, ruthenium, gold, etc.). The compound constituting the active material may be a crystalline structure or an amorphous body.
The positive electrode active material (the above nickel compound or the like) is preferably a fine particle having an average particle size of about 1 nm or more and 10 nm or less based on electron microscope observation or laser diffraction / light scattering method, but an average particle size larger than this (for example, You may use the active material particle which has 10 nm or more and 10 micrometers or less). As additives other than the active material, an appropriate material such as various conductive materials, electrolytes (which may be liquid or gel polymers), binders (binders), depending on either the positive electrode or the negative electrode. ), Solvents, and the like, but those used in various conventional secondary batteries may be used and do not characterize the present invention.
The electrode mixture (positive electrode mixture or negative electrode mixture) is typically prepared into a slurry (paste) by mixing the necessary solid components together with a solvent, and the slurry electrode mixture is adjacent to the current collector. The electrode mixture layer is formed by filling between the body and the current collector (typically including a drying step thereafter). Particularly, a nano-sized fine active material particle of about 10 nm or less and an organic material (organic electrolyte) such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer resin, or the like in a highly dispersed state (a conductive material if necessary) Fine particles may be dispersed.) The use of a positive electrode mixture or a negative electrode mixture containing an inorganic / organic hybrid material present in (1) is preferred.

As described above, the preferred first embodiment of the electrode structure and the current collector disclosed herein has been described with reference to FIG. 2, but is not limited to the forms shown in these drawings. The shape of the current collector disclosed herein is formed so as to extend from one wide plane of the plate electrode structure to the other wide plane in the thickness direction of the structure, and the current collector It is only necessary that the body and the electrode mixture layer can form a mixed state while maintaining a predetermined regularity in the entire region from one end to the other end in one direction orthogonal to the thickness direction. .
For example, as another preferred embodiment (second embodiment), there is a stacked structure as shown in FIG. Specifically, the electrode structure 10B according to the second embodiment shown in FIG. 3 forms a current collector laminated structure obtained by laminating a plurality of sheet-like current collectors 15B in the surface facing direction, An electrode mixture layer (that is, a positive electrode mixture layer) 16B is formed between a plurality of sheet-like current collectors 15A constituting the current collector laminated structure. In other words, the electrode structure 10B according to the present embodiment has a plate shape (sheet) configured such that a plurality of sheet-like current collectors 15B and electrode mixture layers 16B are alternately stacked in the current collector lamination direction. Electrode structure 10B.

According to the electrode structure 10B according to this embodiment having such a structure, the electrode mixture layer 16B can be stably held by being sandwiched between two adjacent sheet-like current collectors 15B. Further, according to the electrode structure 10B having such a stacked structure, the contact area with the current collector 15B per unit volume of the electrode mixture layer 16B can be increased. For this reason, the conductive path between the current collector 15B and the active material in the electrode mixture layer 16B held by the current collector 15B can be increased. Thereby, improvement of battery performance, such as a high rate characteristic, can be aimed at.
In addition, since the electrode structure 10B having a laminated structure according to the present embodiment has a laminated structure in which sheet-like current collectors 15B and electrode mixture layers 16B are alternately laminated, the thickness direction of the plate-like electrode structure 10B is determined. Are mixed while maintaining a predetermined regularity in the entire region from one end to the other end in one direction (here, the long side direction of the wide plane).
As a result, even with the electrode structure 10B according to the present embodiment, there is no bias across the entire electrode structure, and between the current collector 15B and the active material in the electrode mixture layer 16B held by the current collector. The conductive path can be increased.

The volume ratio of the current collector 15B portion in the entire volume of the electrode structure 10B is not particularly limited. From the viewpoint of securing the capacity, it is preferable that the ratio of the electrode mixture layer 16B is high. On the other hand, the volume ratio of the current collector 15B portion is preferably about 70 vol% or more and 90 vol% or less from the viewpoint of forming a good conductive path and exhibiting a quick charge / discharge function.
Further, the thickness of each sheet-like current collector 15B constituting the electrode structure 10B according to the present embodiment may be the same as that of the first embodiment described above. In addition, regarding the shape (long side and short side sizes) of the current collector 15B, in consideration of ion conductivity in the thickness direction of the entire electrode structure 10B, the current collector 15B corresponding to the thickness of the electrode structure 10B The short side length is suitably 0.5 mm or less. Further, the length of the long side of the current collector 15B corresponding to the length in the width direction of the electrode structure 10B orthogonal to the stacking direction is not particularly limited. For example, the aspect ratio (long) It is preferable to define the size so that the side length / short side length is 100 or less (for example, 10 or more and 100 or less).
The means for maintaining the shape of the electrode structure 10B composed of the current collector 15B and the electrode mixture layer 16B, the composition of the current collector 15B and the electrode mixture layer 16B, and the like are the same as in the first embodiment described above. It doesn't have a duplicate explanation.

Another preferred embodiment (third embodiment) includes a spiral structure as shown in FIG. Specifically, the electrode structure 10C according to the third embodiment shown in FIG. 4 is formed in a spiral shape having an outer shape of a rectangular sheet (plate shape) when viewed from the wide plane of the rectangular plate electrode structure 10C. A current collector 15C (hereinafter referred to as “spiral current collector 15C”) and a spiral electrode mixture layer 16C disposed in a spiral groove portion corresponding to the spiral shape of the current collector 15C. ing. By combining these two, one rectangular plate-like electrode structure 10C is formed.
Also in the electrode structure 10C according to the third embodiment, the spiral electrode collector 15C and the spiral electrode mixture layer 16C disposed in the spiral groove corresponding to the spiral shape have the thickness of the plate electrode structure 10C. Mixed in one region orthogonal to the direction (here, either the long side direction or the short side direction of the wide plane) from one end to the other end while maintaining a predetermined regularity. ing.
As a result, even with the electrode structure 10C according to the present embodiment, the current between the current collector 15C and the active material in the electrode mixture layer 16C held by the current collector is uniform throughout the electrode structure. The conductive path can be increased.

As described above, the electrode structures 10A, 10B, and 10C according to some embodiments have been described. However, the secondary battery (for example, the nickel metal hydride battery 100) including these electrode structures as electrodes can be used for various applications. As a suitable application, it is suitable as a structure constituting an electrode of a secondary battery as a driving power source mounted on a vehicle such as an electric vehicle (EV), a hybrid vehicle (HV), and a plug-in hybrid vehicle (PHV). is there.
As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

DESCRIPTION OF SYMBOLS 10 Positive electrode 10A, 10B, 10C Electrode structure 12 Positive electrode current collection tab 14 Positive electrode terminal 15A, 15B, 15C Current collector 16A, 16B, 16C Electrode compound layer (positive electrode compound layer)
17A, 17B Bent top end portion 19 Guide member 20 Negative electrode 30 Separator 40 Case 42 Lid 50 Gasket 60 Spacer 100 Secondary battery (nickel metal hydride battery)

Claims (1)

An electrode structure used for a positive electrode or a negative electrode of a secondary battery,
The electrode structure is a plate-like structure as a whole,
A current collector constituting at least a part of the plate-like structure, wherein at least a part extends from one wide plane of the plate-like structure in the thickness direction of the plate-like structure to reach the other wide plane. One or more current collectors formed in
An electrode mixture layer in contact with the current collector;
Have
Here, the current collector and the electrode mixture layer have predetermined regularity in the entire region from one end to the other end in one direction orthogonal to the thickness direction of the plate-like structure. An electrode structure characterized by being mixed while being held.

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