JP6738522B2 - 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 or a lithium secondary battery.

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

As mentioned above, the secondary battery used as a driving power source is required to have a performance (high rate characteristic) that enables rapid charging/discharging, and therefore improvement is required from various viewpoints regarding the configuration of the secondary battery. It is being appreciated. One approach for that purpose is to study and improve the configuration and structure of the electrode.
In particular, in order to increase the battery capacity and realize even more rapid transfer of ions and electrons between electrodes, research is being actively 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 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 Document 1 discloses a secondary battery including a zinc negative electrode configured 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

However, the technique disclosed in Patent Document 1 more stably holds the negative electrode mixture containing the negative electrode active material (and the positive electrode mixture containing the positive electrode active material) on the negative electrode current collector (and the positive electrode current collector). It is not related to letting. Further, in addition to ensuring stable holding power of the positive electrode mixture and the negative electrode mixture to the positive and negative electrode current collectors, in order to improve the high rate characteristics and the like, the positive electrode mixture material or the negative electrode held by the current collectors is used. It is necessary to form a good electron conduction path or ion conduction path (hereinafter collectively referred to as “conductive path”) between the active material in the mixture and the current collector. In particular, when using a positive electrode composite material or negative electrode composite material 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 and the like, it is important to stably hold the mixture on the current collector and to construct a good conductive path between the active material in the mixture and the current collector.
Therefore, the present invention was created to solve such problems, and is intended to provide a stable current collector (positive electrode current collector or negative electrode current collector) of an electrode mixture (positive electrode mixture or negative electrode mixture). In addition to holding the above, it is an object of the present invention to provide an electrode structure capable of forming a good conductive path between the current collector and the active material in the electrode mixture held by the current collector.

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.
In the plate-shaped structure, the sheet-shaped current collectors are stacked in the face-to-face direction (that is, the sheet surfaces of the adjacent sheet-shaped current collectors (the widest face; the same applies hereinafter) face each other). It has a current collector laminated structure (to be laminated) and an electrode mixture layer formed between the sheet-shaped current collectors constituting the current collector laminated structure.

In the electrode structure having such a configuration, a plate-shaped (also referred to as thin plate-shaped or sheet-shaped) electrode structure is a current collector laminated structure in which a plurality of sheet-shaped current collectors are laminated in a face-to-face direction, and the laminated structure. And an electrode mixture layer formed in a state of being sandwiched between the sheet-shaped current collectors constituting the. In other words, the electrode structure that is macroscopically plate-shaped in this configuration has the above-described current collector laminated structure and the sheet-shaped current collector that constitutes the laminated structure when the constituent elements are viewed microscopically. It has a repeating structure with the electrode mixture layer formed between them.
As a result, in the electrode structure having this configuration, the electrode mixture layer can be stably held by being sandwiched between the two adjacent sheet-shaped current collectors. Therefore, according to the electrode structure of the present configuration, for example, a plate-shaped electrode structure having the same volume, and a sheet-shaped electrode structure having one or both of the surfaces of the electrode mixture layer formed in one sheet-like shape is collected. The conductive path between the current collector and the active material in the electrode mixture layer held by the current collector can be increased as compared with the conventional plate-shaped electrode structure in which the current collector is arranged. ..
Therefore, according to the present invention, it is possible to realize the provision of an electrode structure that contributes to the improvement of the holding stability of the electrode mixture and the improvement of the battery performance such as the high rate characteristic.

Further, in a preferred embodiment of the electrode structure disclosed herein, the current collector laminated structure is formed by one current collector member having a corrugated fin shape (that is, a zigzag corrugated plate shape). Characterize.
According to such a configuration, the above-described effects can be achieved, and since the current collector laminated structure is integrally formed by one corrugated fin-shaped current collector member, the shape stability of the electrode structure itself can be improved. It can be improved.

Further, in a preferred embodiment of the electrode structure disclosed herein, the current collector laminated structure is constrained in the stacking direction of the sheet-shaped current collector (referred to as the face-opposing direction, hereinafter the same). The restraint member is attached.
With such a configuration, it is possible to further improve the stability of the form of the current collector laminated structure in which the plurality of sheet-shaped current collectors described above are laminated in the surface facing direction.

It is a partially broken (perspective) perspective view schematically showing an embodiment of a secondary battery (nickel hydrogen battery) equipped with the electrode structure disclosed herein as a positive electrode or a negative electrode. It is a perspective view which shows typically the whole structure of the electrode structure which concerns on one Embodiment. It is a figure which illustrates typically a part of structure of the electrode structure shown in FIG. It is a perspective view which shows typically the whole structure of the electrode structure which concerns on other one Embodiment.

Hereinafter, some suitable embodiments of the electrode structure disclosed herein will be described with reference to the drawings.
Matters other than the matters particularly referred to in the present specification and necessary for carrying out the present invention (for example, the general configuration and manufacturing process of the entire secondary battery that do not characterize the present invention) are not related to the related art. It can be understood as a design matter of those skilled in the art based on the related art. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field. In addition, 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 the present 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 power storage elements such as so-called storage batteries and electric double layer capacitors.
In addition, the “electrode mixture” means a composition (composite material) containing an active material of any one of predetermined positive and negative electrodes, and the contents of the active material and other components (various additives) constituting the mixture material are , Nickel-metal hydride battery, lithium secondary battery, etc.
Therefore, the electrode composite material layer (specifically, the positive electrode composite material layer or the negative electrode composite material layer) is a layer mainly composed of an active material formed by applying the electrode composite material 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 of the electrode mixture layer (active material layer) are necessarily the same. is not. For example, when an organic solvent is contained in the electrode mixture, it is usual that the organic solvent is evaporated and lost when the electrode mixture layer is formed. 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 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. 1.
As shown in FIG. 1, the nickel-hydrogen battery 100 according to this embodiment includes a case 40 including a lid 42. The case 40 accommodates the positive electrode 10, the negative electrode 20, and the separator 30 that form the electrode body of the nickel-hydrogen battery 100 according to the present embodiment.
The positive electrode 10 is composed of a plurality of thin plate-shaped (sheet-shaped) electrode structures, which are electrically connected to a positive electrode terminal 14 via a positive electrode current collector tab 12. On the other hand, the negative electrode 20 is composed of a plurality of thin plate-shaped (sheet-shaped) electrode structures, which are provided on the bottom surface of the case 40 via a negative electrode current collecting member (not shown). (Not shown). Further, a spacer 60 and a gasket 50 provided around the spacer are mounted inside the case 40 with respect to the lid 42, and maintain a sealed state inside the case 40.
The spacer 60 is provided 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, it may be similar to that attached to the conventional nickel-hydrogen battery, and since it is not a structure that characterizes the present invention, further detailed description will be omitted. The material and shape of each component (positive and negative electrodes, separator, case, etc.) of the nickel-hydrogen battery 100 are similar to those of the conventional one except the part to which the electrode structure 10A disclosed herein is applied. The nickel-metal hydride battery may be the same as the nickel-hydrogen battery and does not particularly characterize the present invention.

Next, the electrode structure 10A according to this embodiment will be described in detail with reference to FIGS. 2 and 3. The electrode structure 10A according to the present embodiment is a structure that constitutes the positive electrode 10 in the nickel hydrogen battery 100 shown in FIG. As shown in FIG. 2, the electrode structure 10A according to the present embodiment which constitutes the positive electrode 10 has a plate-like (sheet-like) shape as a whole. In the drawings, the size, shape, etc. (particularly the thickness) are deformed for the sake of explanation.
More specifically, the electrode structure 10A according to the present embodiment includes a current collector laminated structure 17A obtained by laminating a plurality of sheet-shaped current collectors 15A in a surface facing direction thereof, and the current collector laminated body. It has an electrode mixture layer (that is, a positive electrode mixture layer) 16A formed between a plurality of sheet-shaped current collectors 15A constituting the structure 17A.
In other words, the electrode structure 10A according to the present embodiment has a plate shape (sheets) configured by alternately stacking a plurality of sheet-shaped current collectors 15A and electrode mixture layers 16A in the current collector stacking direction. State) structure.
According to the electrode structure 10A of this embodiment having such a structure, the electrode mixture layer 16A can be stably held by being sandwiched between the two adjacent sheet-shaped current collectors 15A. Further, according to the electrode structure 10A having such a structure, the contact area with the current collector 15A per unit volume of the electrode mixture layer 16A can be increased. Therefore, the conductive path between the current collector 15A and the active material in the electrode mixture layer 16A held by the current collector 15A can be increased. As a result, it is possible to improve battery performance such as high rate characteristics.

The shape of the current collector 15A is not limited to the flat shape as illustrated, as long as it has a sheet-like structure and can fill the electrode mixture layer 16A between two adjacent current collectors 15A. .. For example, the entire current collector is curved, or a part of the current collector is bent (for example, 50% or less of a rectangular current collector sheet is parallel to the long side. The shape may be such that it is bent at an angle of not more than 30 degrees (preferably not more than 30 degrees).There is no particular limitation on the surface structure, and a completely flat surface structure may be used, but it is necessary to have an appropriate uneven structure for the electrode surface. It is preferable from the viewpoint of increasing the contact area with the material layer 16A.

The size of the sheet-shaped 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, 10 μm or more and 50 μm or less. A degree is suitable. Regarding the shape (size of the long side and the short side) of the current collector 15A, considering the ion conductivity in the thickness direction of the entire electrode structure 10A, the short side of the current collector 15A corresponding to the thickness of the electrode structure 10A. A length of 0.5 mm or less is suitable. The length of the long side of the current collector 15A, which corresponds to the length in the width direction of the electrode structure 10A orthogonal to the stacking direction, is not particularly limited, but for example, the aspect ratio (long The size is preferably specified 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 current collector laminated structure 17A is not particularly limited, and includes, for example, an appropriate amount of binder (binder) in the electrode mixture material arranged (filled) between the sheet-shaped current collectors 15A. Alternatively, the electrode mixture layer 16A may have a function as an adhesive layer for holding the current collector laminated structure 17A.
Preferably, as shown in FIG. 2, the current collector laminated structure 17 is constrained by some constraining member 18. For example, a tape (or string)-shaped restraining member 18 as shown in the drawing can be employed. The constraining member 18 having such a form (an insulating tape-like constraining member is preferable) is attached to the outer peripheral surface of the current collector laminated structure 17, and tension is applied in the laminating direction to laminate the current collector. Structural stabilization of the structure 17, and by extension, the electrode structure 10A itself can be realized at a high level. The mounting position of the restraint member 18 is not limited to the mode shown in FIG. For example, although not shown, a needle-shaped (thin rod-shaped or string-shaped) restraint member is passed through the inside of the current collector laminated structure 17 in the stacking direction (for example, near the center of the sheet surface of the sheet-shaped current collector 15A). The needle-shaped restraint member may be penetrated at one place or a few places.), and a tension may be applied between one end face and the other end face of the current-collector laminated structure 17 in the laminating direction. .. Alternatively, instead of the tape-shaped restraining member 18, a screw member capable of tightening the current collector laminated structure 17A in the laminating direction may be mounted. Alternatively, a method of winding the outer periphery of the current collector laminated structure 17 with an elastic body (rubber material), a heat-shrinkable material, or a fibrous or net-shaped member may be adopted.

Alternatively, as shown in FIG. 3, a convex portion 15C protruding substantially vertically is provided on a part of one surface (for example, a part of the peripheral portion) of the sheet-shaped current collector, and the surface on the opposite side of the convex portion 15C. It is also preferable to provide a concave portion 15D into which the convex portion 15C is fitted. By providing such unevenness, when a plurality of sheet-shaped current collectors 15A are stacked, the convex portion 15C of one stacked current collector 15A has a concave portion 15D of the other facing current collector 15A. To fit. As a result, the stacked sheet-shaped current collectors 15A are constrained to each other, and positional deviation can be prevented to form a stable current collector laminated structure 17A. Furthermore, by providing the irregularities, it becomes easy to provide an appropriate gap between the adjacent current collectors 15A. For example, the protrusion length of the convex portion 15C is 0.5 times or more and 10 times or less, preferably 1 time or more and 5 times or less, or 5 times or more and 10 times or more the thickness of the sheet-shaped current collector 15A. It can be set to:

The metal composition of the sheet-shaped current collector 15A for forming the current collector laminated structure forming the skeleton of the electrode structure 10A according to the present embodiment is as long as a conductive path with the electrode mixture layer 16A can be constructed. There is no particular limitation. 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-hydrogen battery, typically nickel or an alloy mainly containing nickel, or the like can be given. It may be a porous metal member (for example, a punching metal member used for an electrode plate of a conventional nickel hydrogen battery).
Further, the current collector 15A used may be magnetized. Each current collector 15A may be magnetized after the current collector laminated structure 17A is constructed. By being magnetized, the stability of the laminated structure itself can be further improved.

Further, the volume occupancy of the current collector laminated structure 17 in the entire volume of the electrode structure 10A (that is, the volume ratio excluding the electrode mixture layer 16A) is preferably 70 vol% or more and 90 vol% or less. When the volume occupancy of the current collector laminated structure 17 is within this range, a good conductive path is formed, and a rapid charge/discharge function can be exerted.
Alternatively, a guide member (preferably a plate member, see FIG. 4 relating to an embodiment described later) is provided on the stacking surface of the current collector stacked structure 17A (preferably a wide stacking surface on the long side of the sheet-shaped current collector 15A). ) May be provided. By attaching the guide member, the structural stability can be further improved. When the guide member is made of a conductive member capable of collecting current, it can function as a current collecting portion (collector) of the electrode.

On the other hand, the structure of the electrode mixture layer 16A is not particularly limited, and any one of various positive and negative electrodes of a type required depending on the type of the target secondary battery such as a nickel hydrogen 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 for a nickel-hydrogen battery, an active material containing at least one nickel compound selected from nickel hydroxide, nickel oxyhydroxide, and derivatives thereof 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 with another metal element (cobalt, aluminum, zinc, manganese, tungsten, titanium, niobium, ruthenium, gold, etc.). The compound forming the active material may be a crystalline structure or an amorphous body.
The positive electrode active material (such as the nickel compound) is preferably fine particles having an average particle size of 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 (eg, Active material particles having a size of 10 nm or more and 10 μm or less) may be used. As the additive other than the active material, an appropriate material, for example, various conductive materials, electrolytes (which may be liquid or gel polymers), binders (binders) depending on whether the positive electrode or the negative electrode is used. ), a solvent, and the like, but those used in various types of conventional secondary batteries may be used and do not characterize the present invention, so further detailed description will be omitted.
The electrode composite material (positive electrode composite material or negative electrode composite material) is typically prepared by mixing necessary solid components together with a solvent to prepare a slurry (paste), and the slurry-like electrode composite is provided with an adjacent collector. The electrode mixture layer is formed by filling between the body and the current collector (typically including a drying step thereafter). Particularly, nano-sized fine active material particles of about 10 nm or less and an organic material (organic electrolyte) such as polyvinyl alcohol or ethylene-vinyl alcohol copolymer resin are in a highly dispersed state (further, if necessary, a conductive material). It is preferable to use a positive electrode composite material or a negative electrode composite material containing an inorganic/organic hybrid material present in the fine particles may be dispersed).

Although a preferred embodiment of the electrode structure and the current collector laminated structure disclosed herein has been described above with reference to FIGS. 2 and 3, the present invention is not limited to the forms shown in these drawings. For example, as another preferred embodiment, like the electrode structure 10B (current collector laminated structure 17B) shown in FIG. 4, the sheet-shaped current collector 15B has one corrugated fin shape (zigzag corrugated plate shape). It may be formed of a current collector member. Also in this case, the electrode mixture layer 16B can be formed by including a predetermined electrode mixture between the adjacent sheet-shaped current collectors (that is, the call gate fins) 15B.
In such a configuration, the sheet-shaped current collector 15B is configured from one corrugated fin-shaped member, and the integrated current collector laminated structure 17B is obtained. Therefore, the shape stability of the electrode structure 10B itself can be further improved.
Further, as shown in the figure, also in the present embodiment, the guide member (current collecting portion) 19 can be provided on the laminated surface of the current collector laminated structure 17B. By additionally providing the guide member 19, it is possible to further improve the structural stability and improve the efficiency of collecting current from the current collector 15B.

The nickel-hydrogen battery 100 according to the present embodiment can be used for various purposes, and as a suitable use, it is mounted on a vehicle such as an electric vehicle (EV), a hybrid vehicle (HV), and a plug-in hybrid vehicle (PHV). It is suitable as a structure that constitutes an electrode of a secondary battery as a driving power source.
Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

10 Positive electrode 10A Electrode structure 10B Electrode structure 12 Positive electrode current collector tab 14 Positive electrode terminal 15A, 15B Sheet-shaped current collector 15C Convex portion 15D Recessed portion 16A, 16B Electrode mixture layer (positive electrode mixture layer)
17A, 17B Current collector laminated structure 18 Restraint member 19 Guide member 20 Negative electrode 30 Separator 40 Case 42 Lid 50 Gasket 60 Spacer 100 Secondary battery (nickel hydrogen battery)

Claims (2)

An electrode structure used for a positive electrode or a negative electrode of a secondary battery,
The electrode structure is a plate-shaped structure as a whole,
The plate-shaped structure is
A sheet-shaped current collector, a current collector laminate structure formed by one corrugated fin-shaped current collector and laminated in a surface facing direction,
A plurality of electrode mixture layers arranged respectively between the laminated current collectors ,
Has
Here, each of the electrode mixture layer is sandwiched between two adjacent sheet-shaped current collectors of the current collector laminated structure,
The sheet-shaped current collector and the electrode mixture layer are configured to be alternately stacked in the current collector stacking direction (provided that the normal to the surface having the maximum area in the stacking direction and the structure). (Except for a mode in which the directions match), an electrode structure. The electrode structure according to claim 1, further comprising a restraint member that restrains the current collector laminated structure.

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