JP2019114400A - Power storage device - Google Patents

Abstract

To ensure high energy density and high output density in a power storage device.SOLUTION: A power storage device includes: a positive electrode system comprising a first positive electrode 10 including a first positive electrode collector 12 and a first positive electrode mixture layer 14 and a second positive electrode 20 including a second positive electrode collector 22 and a second positive electrode mixture layer 24 of a material that is different from that of the first positive electrode mixture layer 14; and a negative electrode system 50 disposed between the first positive electrode 10 and the second positive electrode 20. The negative electrode system 50 includes: a negative electrode collector 54; a first negative electrode mixture layer 52a provided on one surface of the negative electrode collector 54 to face a fist positive electrode 10 side; and a second negative electrode mixture layer 52b provided on the other surface of the negative electrode collector 54 to face a second positive electrode 20 side. The active material of the first negative electrode mixture layer 52a is different from the active material of the second negative electrode mixture layer 52b.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device.

  Power storage device (hybrid capacitor) combining a positive electrode in a lithium ion battery and a positive electrode used in an electric double layer capacitor and a negative electrode in a lithium ion battery as a method for improving the output density in the power storage device It has been known. For example, Patent Document 1 discloses a capacitor positive electrode in which a capacitor positive electrode layer containing fine particles of activated carbon is formed on one surface of a capacitor positive electrode current collector foil, and a negative electrode on one surface of a negative electrode current collector foil having through holes. A battery positive electrode comprising particles of a lithium-containing metal compound on one side of a battery positive electrode current collector foil, a first negative electrode sandwiched between a common negative electrode formed with layers, a capacitor positive electrode layer and a negative electrode layer A power storage device cell comprising a battery positive electrode formed with a layer, and a second separator sandwiched between a negative electrode current collector foil and a battery positive electrode layer, wherein the common negative electrode is common to the capacitor positive electrode and the battery positive electrode. The power storage device cell is described in which the second separator is in contact with the other side of the negative electrode current collector foil. In addition, Patent Document 2 includes a positive electrode system configured by a positive electrode including a current collector and a positive electrode mixture layer, and a negative electrode system configured by a negative electrode including a current collector and a negative electrode mixture layer. A positive electrode system having a first positive electrode including a first positive electrode mixture layer and a second positive electrode including a second positive electrode mixture layer; and a negative electrode system including a first positive electrode and a second positive electrode The first positive electrode mixture layer includes a transition metal oxide, and the second positive electrode mixture layer includes activated carbon, and the first positive electrode mixture layer and the second positive electrode mixture have a negative electrode disposed therebetween. It is described that a through-hole is formed in the current collector of the negative electrode disposed between the material layer.

Patent No. 5040626 Patent No. 5091573

  In the hybrid capacitors as described in Patent Documents 1 and 2, different types of positive electrodes such as a positive electrode of a lithium ion battery and a positive electrode of an electric double layer capacitor exist as a positive electrode corresponding to the negative electrode (common negative electrode). There is a problem that it is difficult to select the material of the negative electrode that meets the requirements of both the power density and the power density. For example, the irreversible capacity of the negative electrode may increase, or the electrode density may not be increased, and the volume of the cell may increase.

  The present invention has been made in view of such background, and an object of the present invention is to provide a power storage device capable of securing high energy density and power density.

  One embodiment of the present invention for achieving the above object comprises a first positive electrode including a first positive electrode current collector and a first positive electrode mixture layer, a second positive electrode current collector, and the first positive electrode mixture layer and materials. A positive electrode system including a second positive electrode including a different second positive electrode mixture layer, and a negative electrode system disposed between the first positive electrode and the second positive electrode. The negative electrode system includes a negative electrode current collector, a first negative electrode mixture layer provided on one surface of the negative electrode current collector facing the first positive electrode side, and the other of the negative electrode current collector. And a second negative electrode mixture layer provided on the surface to face the second positive electrode side, and the material of the first negative electrode mixture layer is different from the material of the second negative electrode mixture layer. .

  As in the present invention, the negative electrode system is provided on one side of the negative electrode current collector so as to face the first positive electrode side, and the other side of the negative electrode current collector is on the second positive electrode side. And a second negative electrode material mixture layer provided opposite to the first negative electrode material mixture layer, and the material of the first negative electrode material mixture layer is different from the material of the second negative electrode material mixture layer. (1) A storage device having high energy density and power density can be configured to match the characteristics of the electrode system consisting of the negative electrode on the positive electrode side and the electrode system consisting of the negative electrode on the second positive electrode side and the second positive electrode .

  For example, the active material of the first negative electrode mixture layer includes an active material constituting a negative electrode of a battery, and the active material of the second negative electrode mixture layer includes an active material constituting a negative electrode of an electric double layer capacitor. As a result, an electric storage device having a high electrode density (energy density) can be realized by the electrodes of the first negative electrode mixture layer and the first positive electrode mixture layer, and by the electrodes of the second negative electrode mixture layer and the second positive electrode mixture layer, It is possible to realize an electricity storage device with high response and large output density. As described above, according to the present invention, high energy density and power density can be secured in the power storage device.

  The active material of the first negative electrode mixture layer contains graphite, and the active material of the second negative electrode mixture layer contains graphite which is adhered by pitch. As described above, by using graphite adhered by the pitch as the active material of the second negative electrode mixture layer, the response in the electrode system including the second positive electrode and the negative electrode on the second positive electrode side is improved, and the output density is increased. Particularly high power storage devices.

  Also, for example, the active material of the first positive electrode mixture layer includes a transition metal oxide, and the active material of the second positive electrode mixture layer includes activated carbon. By doing this, the electrode system comprising the first positive electrode and the negative electrode on the first positive electrode side becomes an electrode system having a high electrode density like a lithium ion secondary battery, and from the negative electrode on the second positive electrode and the second positive electrode side Since the electrode system can be an electrode system having a high output density like a lithium ion capacitor, high energy density and output density can be secured. In addition, the durability as an electricity storage device is not impaired.

  According to the present invention, high energy density and power density can be ensured. Other effects will be clarified in the following description.

FIG. 1 is a diagram showing an example of the configuration of a power storage device 100 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an internal structure of a comparative example 1 sample.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(overall structure)
FIG. 1 is a cross-sectional view schematically showing an example of the internal structure of a power storage device 100 according to an embodiment of the present invention. As shown in the figure, the electricity storage device 100 includes a positive electrode system including the first positive electrode 10 and the second positive electrode 20, and a negative electrode system 50 provided between the first positive electrode 10 and the second positive electrode 20. Storage device.

  The first positive electrode 10 has a foil-like first positive electrode current collector 12 and a first positive electrode mixture layer 14 formed by coating or the like on this surface. The second positive electrode 20 includes a foil-like second positive electrode current collector 22 and a second positive electrode mixture layer 24 formed by coating or the like on this surface.

  On the other hand, the negative electrode system 50 includes a foil-like negative electrode current collector 54 and a negative electrode mixture layer 52. The negative electrode mixture layer 52 includes a first negative electrode mixture layer 52a and a second negative electrode mixture layer 52b. The first negative electrode mixture layer 52a is applied to the surface of the negative electrode current collector 54 on the first positive electrode 10 side. It is formed by being done. The second negative electrode mixture layer 52 b is formed by coating or the like on the surface of the negative electrode current collector 54 on the second positive electrode 20 side. The first negative electrode mixture layer 52 a faces the first positive electrode mixture layer 14 via the separator 30, and the second negative electrode mixture layer 52 b faces the second positive electrode mixture layer 24 via the separator 40.

  The first positive electrode 10, the second positive electrode 20, and the negative electrode system 50 are accommodated in a predetermined packaging material 70 (for example, a laminate film or a metal can), and the electrolytic solution 80 is injected into the packaging material 70 and sealed.

  In addition, the first positive electrode current collector 12 and the second positive electrode current collector 22 electrically connected to each other by the lead wire 60 are connected to the lead wire 60 via the lead wire 62 to form a predetermined circuit 200 (for example, a charger Wire connected to the negative electrode current collector 54 of the negative electrode system 50, while the negative electrode terminal 202 of the circuit 200 is electrically connected to the positive electrode terminal 201 of the Are electrically connected to the negative electrode system 50.

The positive electrode active material of the first positive electrode mixture layer 14 is, for example, an active material constituting a positive electrode of a battery, and specifically, for example, activated carbon, transition metal oxide or the like used for a lithium ion battery. More specifically, for example, lithium cobaltate (LiCoO ₂ ), lithium-containing metal oxides, transition metal oxides or sulfides such as cobalt, manganese, vanadium, titanium, nickel and the like.

  The positive electrode active material of the second positive electrode mixture layer 24 is, for example, an active material constituting a positive electrode of an electric double layer capacitor, and specifically, for example, a positive electrode active material (eg, activated carbon) used in a lithium ion capacitor It is.

  The material of the first positive electrode current collector 12 and the second positive electrode current collector 22 is, for example, an electrode of aluminum, stainless steel or the like.

  The material of the negative electrode current collector 54 is, for example, an electrode of stainless steel, copper, nickel or the like.

  Here, in the negative electrode mixture layer 52 of the present embodiment, the negative electrode active material of the first negative electrode mixture layer 52a and the negative electrode active material of the second negative electrode mixture layer 52b are different.

  The negative electrode active material of the first negative electrode mixture layer 52a is, for example, an active material constituting the negative electrode of the battery, and specifically, for example, a carbon-based material (for example, graphite) used for the negative electrode of a lithium ion battery Tin oxide, silicon oxide, etc.

  The negative electrode active material of the second negative electrode mixture layer 52b is, for example, an active material constituting a negative electrode of an electric double layer capacitor, and specifically, is a carbon-based material used for a negative electrode of a lithium ion capacitor, for example. The negative electrode active material of the second negative electrode mixture layer 52b is, for example, a carbon-based material (graphite or the like) coated with a pitch, such as hard carbon, and in the case of graphite, for example, pitch coated graphite, amorphous coated graphite It is.

  The combination of the negative electrode active material of the first negative electrode mixture layer 52a and the material of the negative electrode active material of the second negative electrode mixture layer 52b is constituted by the first positive electrode mixture layer 14 and the first negative electrode mixture layer 52a. Determined based on the response of the electrode reaction required for each of the electrode system and the electrode system composed of the second positive electrode mixture layer 24 and the second negative electrode mixture layer 52b, the power density, the energy density, etc. Specifically, for example, factors such as the particle size, specific surface area, and degree of crystallinity of each material are considered.

  For example, the particle diameter of the negative electrode active material of the second negative electrode mixture layer 52b is increased in order to increase the output density to correspond to the second positive electrode mixture layer 24 to improve the response or reduce the irreversible capacity. Select a material that is small or has a large specific surface area. The negative electrode active material of the first negative electrode mixture layer 52a is selected to have a larger particle diameter or a smaller specific surface area in order to improve the electrode density (energy density) or to increase the electric capacity. Thus, the power storage device 100 as a whole becomes a power storage device satisfying the required performance of the output density and the power density.

  Subsequently, the separators 30 and 40 are non-woven fabrics having no electron conductivity, and are fibers made of, for example, cellulose, polyethylene or polypropylene.

The electrolytic solution 80 is a solution having electrical conductivity, and is, for example, an electrolytic solution containing a lithium salt. The lithium salt in this case is, for example, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ . Further, the solvent of the electrolytic solution is, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate.

<< evaluation experiment >>
As described above, in the electricity storage device 100 of the present embodiment, the negative electrode active material of the first negative electrode mixture layer 52a and the negative electrode active material of the second negative electrode mixture layer 52b are different. Hereinafter, an evaluation experiment performed by the present inventors in order to examine the energy density of the electricity storage device 100 configured as described above will be described.

1. Sample Preparation First, based on the configuration of the power storage device 100 shown in FIG. 1, samples of two types of lithium ion batteries (Example 1 sample, Comparative Example 1 sample) described below were prepared.

<Preparation of Example 1 Sample>
Example 1 The sample is an electricity storage device using different active materials in the first negative electrode mixture layer 52a and the second negative electrode mixture layer 52b. The constituent materials of the sample of Example 1 were produced as follows.

(First positive electrode system)
As the first positive electrode current collector 12 in the first positive electrode 10, an aluminum foil pressed with aluminum was used. A slurry of LiFePO ₄ (corresponding to the first positive electrode mixture layer 14), which is a positive electrode active material of a lithium ion battery, is coated on one surface of this aluminum foil at a thickness of 65 μm, and a 5.0 cm × 3.0 cm rectangle By cutting a portion (excluding the terminal welding portion), a first positive electrode 10 (positive electrode) having a capacity of 27.6 mAh was obtained.

(2nd positive electrode system)
An aluminum foil pressed with aluminum was used as the second positive electrode current collector 22 in the second positive electrode 20. By applying activated carbon (corresponding to the second positive electrode mixture layer 24) to a thickness of 90 μm on one side of this aluminum foil and then cutting a 5.0 cm × 3.0 cm rectangular portion (except for the terminal welding portion) from this. The second positive electrode 20 (positive electrode) having a capacity of 3.5 mAh was obtained.

(Anode type)
First, copper foil (15 μm in thickness) pressed with copper was used as the negative electrode current collector 54 in the negative electrode system 50. 100 parts by weight of artificial graphite which is a negative electrode active material of a lithium ion battery, 1.5 parts by weight of a thickener, and 1.5 parts by weight of a binder on one side of this copper foil The first negative electrode mixture layer 52a (corresponding to the negative electrode of a lithium ion battery) was produced by applying 59 g / m ² , a thickness of 39.3 μm, and a density of 1.5 g / cm ³ . In addition, on the other side of the copper foil, 100 parts by weight of pitch-coated graphite, which is a negative electrode active material of a lithium ion capacitor, 5.5 parts by weight of a conductive material, 2.0 parts by weight of a thickener, and a binder A mixed solution of 5.0 parts by weight of the slurry is coated to give a single-sided basis weight of 21 g / m ² , a thickness of 27.3 μm, and a density of 0.77 g / cm ³ to form a second negative electrode mixture layer 52 b (a negative electrode of lithium ion capacitor Corresponding to the above). Then, after drying these, they were cut out at 5.2 cm × 3.2 cm (excluding the terminal welded portion) to obtain a negative electrode system 50 (negative electrode).

(Separator)
A 35 μm-thick non-woven fabric made of cellulose was used as the separators 30 and 40.

  The above constituent materials were stacked in the order of the first positive electrode 10, the separator 30, the negative electrode system 50, the separator 40, and the second positive electrode 20 to fabricate a sample of Example 1 of the laminate (electric storage device 100).

Preparation of Comparative Example 1 Sample
The comparative example 1 sample uses the same active material in the first negative electrode mixture layer 52a and the second negative electrode mixture layer 52b as in the conventional power storage device.

  FIG. 2 is a cross-sectional view schematically showing an internal structure of a comparative example 1 sample. First, constituent materials of the sample of Comparative Example 1 were produced as described below.

(First positive electrode)
A first positive electrode 10 similar to the sample of Example 1 was produced.

(Second positive electrode)
A second positive electrode 20 similar to the sample of Example 1 was produced.

(Negative electrode system 50)
First, copper foil (15 μm in thickness) pressed with copper was used as the negative electrode current collector 54 in the negative electrode system 50. 100 parts by weight of pitch-coated graphite as a negative electrode active material for lithium ion capacitors, 5.5 parts by weight of a conductive material, 2.0 parts by weight of a thickener, and 5.0 parts by weight of a binder on both sides of this copper foil The mixed slurry is coated so as to have a single-sided basis weight of 39.5 g / m ² , a thickness (both sides) of 51.3 μm, and a density of 0.77 g / cm ³ to form a negative electrode mixture layer 52 (first negative electrode mixture layer 52a, 2nd negative mix layer 52b) was produced. And after drying this, the negative electrode system 50 (negative electrode) was obtained by cutting out 5.2 cm x 3.2 cm (except for a terminal welding part).

(Separator)
Separators 30 and 40 similar to the sample of Example 1 were produced.

  By stacking the above constituent materials in the order of the first positive electrode 10, the separator 30, the negative electrode system 50, the separator 40, and the second positive electrode 20, a sample of Comparative Example 1 of the laminate (power storage device 100) was produced.

2. Calculation of Volumetric Energy Density Subsequently, the volumetric energy density of each of the sample of Example 1 and the sample of Comparative Example 1 manufactured as described above was calculated. Specifically, the volume of each sample as a laminate was calculated based on the total thickness of each sample and the negative electrode area. And volume energy density was computed from the positive electrode capacity and cell volume of each sample.

3. Experimental Results and Discussion The calculation results of volumetric energy density are shown below.

As shown in this table, the volume energy density (52.4 [mAh / cm ³ ]) of the sample of Example 1 is compared to the volume energy density (47.6 [mAh / cm ³ ]) of the sample of Comparative Example 1 , 10% improvement is seen. From this, by using two different types of negative electrodes as in the sample of Example 1, an electric storage device having a high energy density while securing a high output density by using an electric double layer capacitor (lithium ion capacitor) It turned out that it could be configured.

  As described above, in the electricity storage device 100 of the present embodiment, the negative electrode system 50 is provided with the first negative electrode mixture layer 52 a provided on one surface of the negative electrode current collector 54 so as to face the first positive electrode 10 side. A second negative electrode mixture layer 52b provided on the other surface of the negative electrode current collector 54 so as to face the second positive electrode 20, and the material of the first negative electrode mixture layer 52a is the second Different from the material of the negative electrode mixture layer 52b, an electrode system composed of the first positive electrode 10 and the negative electrode on the first positive electrode 10 side and an electrode system composed of the second positive electrode 20 and the negative electrode on the second positive electrode 20 side The storage device 100 can be configured to have high energy density and power density that match the respective characteristics.

  The active material of the first negative electrode mixture layer 52a is an active material constituting the negative electrode of the battery, and the active material of the second negative electrode mixture layer 52b is an active material constituting the negative electrode of the electric double layer capacitor. As a result, a storage device having a high electrode density (energy density) can be realized by the electrodes of the first negative electrode mixture layer 52 a and the first positive electrode mixture layer 14, and the second negative electrode mixture layer 52 b and the second positive electrode mixture layer 24. The storage device 100 having high response and large output density can be realized by the electrodes according to the above. Thus, according to the storage device 100 of the present embodiment, high energy density and output density can be secured in the storage device.

  Also, the active material of the first negative electrode mixture layer 52a may be graphite, and the active material of the second negative electrode mixture layer 52b may be graphite with adhesion by pitch. As described above, by using graphite adhered by the pitch as the active material of the second negative electrode mixture layer 52b, the responsiveness in the electrode system including the second positive electrode 20 and the negative electrode on the second positive electrode 20 side is enhanced. The power storage device 100 can be configured to have a particularly high output density.

  The active material of the first positive electrode mixture layer 14 may be a transition metal oxide, and the active material of the second positive electrode mixture layer 24 may be activated carbon. By doing this, the electrode system composed of the first positive electrode 10 and the negative electrode on the first positive electrode 10 side becomes an electrode system having a high electrode density like a lithium ion secondary battery, and the second positive electrode 20 and the second positive electrode 20 Since the electrode system comprising the negative electrode on the side can be an electrode system having a high output density like a lithium ion capacitor, a high energy density and a high output density can be secured. In addition, the durability as an electricity storage device is not impaired.

  The above description of the embodiments is for the purpose of facilitating the understanding of the present invention, and does not limit the present invention. The present invention can be modified and improved without departing from the gist thereof, and the present invention includes the equivalents thereof.

100 power storage device, 10 first positive electrode, 12 first positive electrode current collector, 14 first positive electrode mixture layer, 20 second positive electrode, 22 second positive electrode current collector, 24 second positive electrode mixture layer, 30 separator, 40 Separator, 50 negative electrode system, 52 negative electrode mixture layer, 52a first negative electrode mixture layer, 52b second negative electrode mixture layer, 54 negative electrode current collector, 60 conductors, 62 conductors, 64 conductors, 70 packaging materials, 80 electrolyte , 200 circuits, 201 positive terminal, 202 negative terminal

Claims (4)

A first positive electrode comprising a first positive electrode current collector and a first positive electrode mixture layer; a second positive electrode comprising a second positive electrode current collector and a second positive electrode mixture layer different in material from the first positive electrode mixture layer; And a negative electrode system disposed between the first positive electrode and the second positive electrode.
The negative electrode system includes a negative electrode current collector, a first negative electrode mixture layer provided on one surface of the negative electrode current collector facing the first positive electrode side, and the other surface of the negative electrode current collector. And a second negative electrode mixture layer provided facing the second positive electrode side,
An electric storage device characterized in that an active material of the first negative electrode mixture layer is different from an active material of the second negative electrode mixture layer.   The active material of the first negative electrode mixture layer includes an active material constituting a negative electrode of a battery, and the active material of the second negative electrode mixture layer includes an active material constituting a negative electrode of an electric double layer capacitor. The power storage device according to claim 1.   The active material of the said 1st negative mix layer contains graphite, The active material of the said 2nd negative mix layer contains the graphite by which the deposition by pitch was carried out, The said Claim 1 or 2 characterized by the above-mentioned. Power storage device. The active material of a said 1st positive mix layer contains a transition metal oxide, The active material of a said 2nd positive mix layer contains activated carbon, The active material of Claim 1 characterized by the above-mentioned. Storage device.

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