JP6624432B2 - Electrode structure for secondary battery - Google Patents

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 hydrogen battery and a lithium secondary battery.

  Secondary batteries are used as power sources for a wide range of applications. Particularly recently, nickel-metal hydride batteries (a term in a broad sense and includes a nickel-metal hydride battery (Ni-MH) in a narrow sense; the same applies hereinafter), a lithium secondary battery (a so-called lithium ion secondary battery, Rechargeable batteries having 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 have become widespread as power sources for driving hybrid vehicles and the like.

As described above, a secondary battery used as a driving power source is required to have a performance (high-rate characteristic) that enables rapid charging and discharging, and improvements are being made from various viewpoints regarding the configuration of the secondary battery. Has been done. One approach to that is to study and improve the configuration and structure of the electrodes.
In particular, in order to realize an increase in battery capacity and a more rapid transfer of ions and electrons between electrodes, research on improving the composition and shape of the active material for each of the positive and negative electrodes has been actively conducted. In recent years, many attempts have been made to develop a high-performance active material using a hybrid material of an inorganic substance and an organic substance (so-called inorganic / organic hybrid material).
For example, Patent Literature 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 an ion conduction path between the active material in the positive electrode composite material or the negative electrode composite material held by 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 fine active material particles and an organic material (typically, an organic electrolyte) are present in a highly dispersed state, In order to improve the high-rate characteristics, it is important to stably hold the mixture on the current collector and to establish a good conductive path between the active material in the mixture and the current collector.
Therefore, the present invention has been created to solve such a problem, 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. It is intended to provide a possible electrode structure.

The electrode structure disclosed herein 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 forms at least a part of the plate-like structure, and at least a part of the plate-like structure extends in a thickness direction of the plate-like structure from one wide plane of the plate-like structure. It has one or more current collectors formed to extend to the other wide plane, and an electrode mixture layer held by the current collectors.
The current collector and the electrode mixture layer are mixed while maintaining a predetermined regularity in an entire region from one end to the other end in one direction orthogonal to the thickness direction of the plate-shaped structure. It is characterized by doing.

In the electrode structure having such a configuration, the current collector and the electrode mixture layer are mixed while maintaining a predetermined regularity over the entire plate-shaped (thin-plate or sheet-shaped) electrode structure. This means that, in other words, the macroscopically plate-shaped electrode structure of the present configuration has a structure in which the constituent elements are viewed along one direction orthogonal to the thickness direction, and the current collector and the electrode mixture layer And a regular mixed structure.
As a result, in the electrode structure of the present configuration, for example, a plate-shaped electrode structure having the same volume, and a similar sheet-like collection is formed on one or both of the surfaces of the electrode mixture layer formed in one sheet. Compared with a conventional plate-shaped electrode structure in which a current collector is disposed, a conductive path between a current collector and an active material in an electrode mixture layer held by the current collector is entirely formed in the electrode structure. Can be increased without bias.
Therefore, according to the present invention, provision of an electrode structure that contributes to improvement in battery performance such as high-rate characteristics can be realized.

In one preferred embodiment of the electrode structure disclosed herein, the current collector and the electrode mixture layer have one end to the other end in one direction orthogonal to the thickness direction of the plate-shaped structure. Is characterized by being arranged while one sheet-like current collector having a bellows shape (corrugated plate shape) is arranged while maintaining a predetermined regularity in the entire region up to. .
In another preferred embodiment of the electrode structure disclosed herein, the current collector and the electrode mixture layer have one end in one direction perpendicular to the thickness direction of the plate-like structure and the other end. It is realized by a laminated structure in which the sheet-like current collector and the electrode mixture are alternately laminated in the same direction 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 have one end in one direction perpendicular to the thickness direction of the plate-like structure and the other end. The fact that they are mixed while maintaining a predetermined regularity in the entire region up to the end portion is formed in the spirally-shaped current collector and the spirally-shaped groove corresponding to the spirally-shaped current collector when viewed from the wide plane. It is characterized by being realized by the configuration with the arranged electrode mixture.
According to these configurations, improvement in battery performance such as the high-rate characteristics can be suitably realized.

FIG. 2 is a perspective view schematically showing a part of a secondary battery (nickel-metal hydride battery) equipped with the electrode structure disclosed herein as a positive electrode or a negative electrode, which is partially broken (see through). It is a perspective view showing typically the whole structure of the electrode structure concerning a 1st embodiment. It is a perspective view showing typically the whole structure of the electrode structure concerning a 2nd embodiment. It is a perspective view showing typically the whole electrode structure concerning a 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 practicing the present invention (for example, a general configuration and a manufacturing process of the whole secondary battery which does not characterize the present invention) are described in the related art. Can be grasped as a design matter of a person skilled in the art based on the prior art. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. The 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 term “secondary battery” generally refers to a power storage device that can be repeatedly charged and discharged, and is a term that includes a power storage element such as a storage battery and an electric double layer capacitor.
In addition, the “electrode mixture” refers to a composition (mixture) containing an active material of any of the predetermined positive and negative electrodes, and the content of the active material constituting the mixture and other components (various additives) are , A nickel-metal hydride battery, a lithium secondary battery, or the like.
Accordingly, 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 target current collector. (Also referred to as an active material layer), in which the composition of the electrode mixture before being applied to the current collector necessarily matches the composition of the composition constituting the electrode mixture layer (active material layer). is not. For example, when an organic solvent is contained in the electrode mixture, the organic solvent is usually evaporated and lost when the electrode mixture layer is formed, but even in such a case, the electrode mixture is collected. The layer formed by applying it to the body can be referred to as an electrode mixture layer.

First, a box-shaped nickel-metal hydride battery 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) will be briefly described with reference to FIG.
As shown in FIG. 1, the nickel-metal hydride battery 100 according to the present 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 that constitute the electrode body of the nickel-metal hydride battery 100 according to the present embodiment are housed.
The positive electrode 10 is composed of a plurality of thin rectangular plate-shaped (sheet-shaped) electrode structures, which are electrically connected to a positive electrode terminal 14 via a 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 collector (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 are mounted on the inner side of the case 40 with respect to the lid 42, and a sealed state inside the case 40 is maintained.
The spacer 60 has 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, the structure may be the same as that provided for a conventional nickel-metal hydride battery, and is not a structure characterizing the present invention. Also, the material and shape of each component (positive / negative electrode, separator, case, etc.) of the nickel-metal hydride battery 100 are the same as those of the conventional embodiment except for the portion to which the electrode structure 10A disclosed herein is applied. It may be the same as the nickel-metal hydride battery, and does not particularly characterize the present invention, and therefore, a further detailed description will be omitted.

Next, the electrode structure 10A according to the first embodiment will be described in detail with reference to FIG. The 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 the present embodiment constituting the positive electrode 10 has a rectangular plate (sheet) shape corresponding to the shape of the battery case 40 as a whole. In the drawings, the size, shape, and the like (particularly, thickness) are deformed for explanation.
As illustrated, the electrode structure 10A according to the present embodiment is a single rectangular sheet-shaped current collector as its skeleton, and has a predetermined shape in the long side direction so as to have a bellows (corrugated plate) shape. A current collector 15A (hereinafter, referred to as a “bellows-type current collector 15A”) having a shape that is alternately bent at intervals is provided.

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

As described above, in the rectangular plate-shaped 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-shaped electrode structure 10A. In one direction (here, the long side direction of the wide plane) in the entire region from one end to the other end, they are mixed while maintaining a predetermined regularity.
As a result, 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 maintained without bias over the entire electrode structure. The number of conductive paths can be increased.

Note that the form shown in FIG. 2 is merely an example, and the shape of the current collector 15A is such that it extends from one wide plane of the plate-shaped structure 10A in the thickness direction of the plate-shaped structure to the other wide plane. Are formed, and the current collector and the electrode mixture layer maintain a predetermined regularity in the entire region from one end to the other end in one direction orthogonal to the thickness direction. It is sufficient that a mixed state can be formed, and it is not particularly limited to the embodiment shown in FIG. For example, in the embodiment shown in FIG. 2, the bent top ends 17A and 17B are sharply pointed, but may be formed by a gentle arc (R portion).
Also, the surface structure of the current collector 15A is not particularly limited, and may be a completely flat surface structure. However, from the viewpoint of having an appropriate uneven structure, the contact area with the electrode mixture layer 16A increases. preferable. It may be a porous material or a material in which small holes are regularly formed by punching. The angle of the bend 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 degrees ± 15 degrees is preferable.

The size of the current collector 15A may vary depending on the size or shape of the target secondary battery, and is not particularly limited. However, from the viewpoint of current collection efficiency, the thickness is, for example, about 10 μm or more and 50 μm or less. It is suitable.
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 zigzag to be corrugated) may vary depending on the plate shape of the electrode structure. Considering the 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.

Means for maintaining 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 means for retaining (filling) the electrode mixture disposed in the bellows-type current collector 15A may be used. 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 for maintaining 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 kind of restraining member in order to achieve a high level of structural stability of the electrode structure 10A itself. For example, a tape (or string) -shaped restraining member can be employed.

The metal composition of the current collector 15A that forms the skeleton of the electrode structure 10A according to the present embodiment is not particularly limited as long as a conductive path with the 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, an alloy mainly containing nickel, or the like can be used. It may be a porous metal member (for example, a punching metal member used for an electrode plate of a conventional nickel-metal hydride battery).
Further, the current collector 15A used may be magnetic. After the construction of the electrode structure 10A, the bellows-type current collector 15A may be magnetized. By being magnetized, the stability of the laminated structure itself can be further improved.
Alternatively, as shown in FIG. 2, a guide member (preferably a plate-like guide member) 19 may be provided on the electrode structure 10A, preferably along a wide plane. By providing the guide member 19, the structural stability can be improved. Further, when the guide member 19 is made of a conductive member capable of collecting current, it can function as a current collector (collector) of the electrode.

On the other hand, the configuration of the electrode mixture layer 16A is not particularly limited, and may be any one of various types of positive and negative electrodes of a type required according to the type of the target secondary battery, such as a nickel hydride battery and 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 of a nickel-metal hydride battery, at least one nickel compound selected from nickel hydroxide, nickel oxyhydroxide, and their derivatives is contained 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, part of the nickel element may be replaced by another metal element (cobalt, aluminum, zinc, manganese, tungsten, titanium, niobium, ruthenium, gold, etc.). The compound constituting the active material may be a crystalline structure or an amorphous material.
The positive electrode active material (such as the above nickel compound) is preferably a fine particle having an average particle diameter of about 1 nm or more and about 10 nm or less based on observation with an electron microscope or a laser diffraction / light scattering method. Active material particles having a thickness of 10 nm to 10 μm) may be used. As an additive other than the active material, an appropriate material, for example, various conductive materials, electrolytes (which may be liquid or gel polymers), binders (binders) ), A solvent, and the like, but those employed in various conventional secondary batteries may be used, and do not characterize the present invention. Therefore, further detailed description will be omitted.
An electrode mixture (a positive electrode mixture or a negative electrode mixture) is typically prepared in a slurry (paste) by mixing a necessary solid component with a solvent, and the slurry-like electrode mixture is mixed with an adjacent current collector. Filling between the body and the current collector (typically including a drying step thereafter) forms an electrode mixture layer. In particular, a nano-sized fine active material particle of about 10 nm or less and an organic material (organic electrolyte) such as polyvinyl alcohol and ethylene-vinyl alcohol copolymer resin are highly dispersed (if necessary, a conductive material It is preferable to use a positive electrode mixture or a negative electrode mixture containing an inorganic / organic hybrid material which is present in (fine particles may be dispersed).

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 the present invention is not limited to the embodiments shown in the drawings. The shape of the current collector disclosed here is formed so as to extend from one wide plane of the plate-shaped electrode structure in the thickness direction of the structure to reach the other wide plane, and 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, another preferred embodiment (second embodiment) includes a laminated structure as shown in FIG. Specifically, the electrode structure 10B according to the second embodiment shown in FIG. 3 forms a current-collector laminate structure obtained by laminating a plurality of sheet-like current collectors 15B in a direction facing their surfaces, 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 laminate structure. In other words, the electrode structure 10B according to the present embodiment has a plate-like (sheet) configuration in which the plurality of sheet-like current collectors 15B and the electrode mixture layers 16B are alternately stacked in the current-collector stacking direction. ) Of the electrode structure 10B.

According to the electrode structure 10B according to the present 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 laminated structure, the contact area with the current collector 15B per unit volume of the electrode mixture layer 16B can be increased. Therefore, the number of conductive paths 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, the battery performance such as high-rate characteristics can be improved.
In addition, since the electrode structure 10B having a laminated structure according to the present embodiment has a laminated structure in which the sheet-like current collectors 15B and the electrode mixture layers 16B are alternately laminated, the thickness direction of the plate-like electrode structure 10B. 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) orthogonal to.
Accordingly, even with the electrode structure 10B according to the present embodiment, the current between the current collector 15B and the active material in the electrode mixture layer 16B held by the current collector is maintained without bias over the entire electrode structure. The number of conductive paths can be increased.

The volume ratio of the current collector 15B to 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 is preferably about 70 vol% or more and about 90 vol% or less from the viewpoint that a good conductive path is formed and a rapid charge / discharge function is exhibited.
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 above-described first embodiment. Further, regarding the shape (the size of the long side and the short side) of the current collector 15B, considering the ion conductivity in the thickness direction of the entire electrode structure 10B, the shape of the current collector 15B corresponding to the thickness of the electrode structure 10B is considered. 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 lamination direction is not particularly limited. It is preferable to define the size so that (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, and the compositions of the current collector 15B and the electrode mixture layer 16B are the same as those in the first embodiment described above. And do not give duplicate explanations.

As another preferred embodiment (third embodiment), there is a spiral structure as shown in FIG. Specifically, the electrode structure 10C according to the third embodiment shown in FIG. 4 has a rectangular sheet (plate-like) spiral shape when viewed from the wide plane of the rectangular plate-like electrode structure 10C. It is composed of a current collector 15C (hereinafter referred to as a "spiral-type current collector 15C") and a spiral electrode mixture layer 16C disposed in a spiral groove formed corresponding to the spiral shape of the current collector 15C. ing. By combining these two, one rectangular plate-shaped electrode structure 10C is formed.
Also in the electrode structure 10C of the third embodiment, the spiral current collector 15C and the spiral electrode mixture layer 16C arranged in the spiral groove corresponding to the spiral shape have the thickness of the plate-like electrode structure 10C. In one direction perpendicular to the direction (here, either the long side direction or the short side direction of the wide plane), it is mixed while maintaining a predetermined regularity in the entire region from one end to the other end. ing.
Thereby, 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 maintained without bias over the entire electrode structure. The number of conductive paths can be increased.

Although the electrode structures 10A, 10B, and 10C according to some embodiments have been described above, a secondary battery (for example, a nickel-metal hydride battery 100) including the electrode structures as electrodes can be used for various applications. As a preferable 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 mixture layer (positive electrode mixture layer)
17A, 17B Folded top end 19 Guide member 20 Negative electrode 30 Separator 40 Case 42 Cover 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,
One rectangular sheet-like current collector constituting at least a part of the plate-like structure, at least a part of which extends from one wide plane of the plate-like structure in the thickness direction of the plate-like structure and the other thereof. A sheet-like current collector formed to reach the wide plane, and having a spiral shape when viewed from the one wide plane;
An electrode mixture layer that contacts the current collector;
Has,
Here, the electrode mixture layer is formed in a spiral shape disposed in a spiral groove portion corresponding to the spiral shape of the current collector when viewed from the one wide plane, Structure.

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