JP7030766B2 - Electrodes of power storage devices and their manufacturing methods - Google Patents

Description

The present invention relates to electrodes of power storage devices such as secondary batteries and capacitors, and a method for manufacturing the same.

Capacitors and secondary batteries are used in various fields for the purpose of energy reduction and prevention of global warming. Especially in the automobile industry, the adoption of electric energy is accelerating technological development using these.
The electric double layer capacitor has been conventionally used for backing up the memory of an electronic circuit to which a low voltage is applied, and has high input / output reliability as compared with a secondary battery.

For this reason, in recent years, it has been used for power generation by natural energy such as solar power and wind power, construction machinery, power supply for instantaneous reduction, power supply for regeneration of trains, and the like. It has been considered for use in automobiles, but its characteristics and cost do not meet the requirements, and it has not been realized in this field until recent years. However, at present, electric double layer capacitors are used for electronically controlled brake systems, and their applications are being considered for backup power supplies for automobile electrical components, energy supply for starting idling stop systems, brake control, power assist, etc. ..

The structure of the electric double layer capacitor is composed of a positive and negative electrode portion, an electrolytic solution, and a separator that prevents a short circuit between the opposite positive and negative electrode portions. The electrode part is made by kneading a polarized electrode (currently mainly activated carbon), a binder for holding activated carbon, and a conductive auxiliary agent (mainly carbon fine particles), and aluminum foil (thickness about) which is a current collector. It is formed by applying multiple layers on top of 20 μm). Such an electric double layer capacitor is disclosed in, for example, Patent Document 1.

The electric double layer capacitor is charged by moving electrolyte ions in the solution and adsorbing and desorbing on the surface of the fine pores of the activated carbon. The electric double layer is formed at the interface where the activated carbon powder and the electrolytic solution are in contact with each other.
Incidentally, the particle size of ordinary activated carbon is, for example, about 4 to 8 μm, and the specific surface area is, for example, 1600 to 2500 m ³ / g. The electrolytic solution has a cation, an anion, and a solvent, a tetraethylammonium salt as a cation, a borate tetrafluoride ion as an anion, and the like, and a propylene carbonate, an ethylene carbonate, and the like are used as the solvent.

On the other hand, the lithium ion secondary battery is mainly composed of a positive electrode, a negative electrode, and a separator. For example, as shown in FIG. 8, the positive electrode is generally a 20 μm-thick aluminum foil, which is a current collector, kneaded with active material powder, usually lithium cobalt oxide, an additive, a conductive auxiliary agent, and a binder. The negative electrode is a copper foil that is a current collector coated with a carbon material, and these are separated by a separator such as polyethylene and immersed in an electrolytic solution. , Lithium ion secondary battery is configured. Such a lithium ion secondary battery is disclosed in, for example, Patent Document 2.

Charging and discharging is performed by moving lithium ions between the positive electrode and the negative electrode, and during charging, lithium ions move from the positive electrode to the negative electrode, and if the lithium ions in the positive electrode disappear or the negative electrode cannot store lithium ions. Charging is complete. The opposite is true when discharging.

Japanese Unexamined Patent Publication No. 2005-086113 Japanese Unexamined Patent Publication No. 2007-123156

In recent years, the development of capacitors for power devices such as electric vehicles and energy power generation has been promoted. In order to transfer a large amount of energy to and from the capacitor with high efficiency, a method of increasing the capacitance and reducing the internal resistance of the electrode portion can be considered. A simple method is to make the distance between the activated carbon and the aluminum member which is the current collector close to each other and arrange as many activated carbons as possible.

In general, electric double layer capacitors differ from secondary batteries, which are mainly lithium-ion secondary batteries, in that they do not involve chemical reactions, charge is lost over time due to self-discharge, storage time is short, and current is emitted. The point is that the time is short. Regarding the energy density, the lithium battery has several hundred Wh / L, while the electric double layer capacitor has several tens Wh / L. The reason why electric double layer capacitors are being studied not for storage but for backup power supply of electrical components, starting energy of idling stop system, brake control, power assist, etc. is due to the above difference.

Secondary batteries, mainly lithium batteries, have a relatively high energy density and can be used for a long time, so they are used in various fields including mobile devices, and in recent years, they have been used in automobiles, heavy machinery, energy fields, etc. It has become. However, there are still many problems in performance (capacity, charge / discharge speed, life) and manufacturing cost, and the problems are particularly remarkable in large batteries such as automobiles. For example, the current used in a mobile phone is several mA, but the current used in a hybrid vehicle is several hundred A, and the difference between the two is 10,000 times or more. Therefore, it is necessary to increase the size in order to increase the capacity, but there are many problems in increasing the size, such as capacity, charging speed, reliability, and difficulty in manufacturing.

The reaction of the lithium ion secondary battery is a reversible chemical reaction, and the volume of the active material expands and contracts when the electrode is charged and discharged. Therefore, the active material is separated from the current collector and the charge / discharge characteristics are deteriorated. That is, the charge / discharge is not always 100% the same, and the charge / discharge capacity is reduced. Since batteries are used for many years in hybrid vehicles and electric vehicles, it is necessary to suppress the separation of the current collector and the active material in order to prevent the above deterioration.

In addition, the biggest problem with lithium-ion batteries is internal resistance. The internal resistance can be said to be the resistance when lithium ions move in the electrolyte between the positive and negative electrodes inside the battery, but this movement resistance is the main reason why the capacity cannot be increased or the charge / discharge speed cannot be increased. Is.
If a large amount of active material is applied to the current collector to increase the size, the capacity will increase, but the movement resistance will increase. Therefore, there is currently a limit to its thickness. Moreover, the charge / discharge speed is slowed down due to the resistance. When the coating thickness is reduced, the internal resistance is reduced and the charge / discharge speed is increased, but the capacity is reduced. Therefore, it is necessary to stack the current collectors coated with the active material in multiple layers or to expand the area of the current collectors coated with the active material.

The speed of charging and discharging is also due to the amount of lithium ions generated. If many ions are produced at one time and can move at one time, the charging speed and discharging speed will be faster. Since the chemical reaction of the secondary battery occurs at the interface with the electrolyte, if the contact area between the electrode and the electrolyte can be increased, the charge / discharge rate will also be improved.

In order to reduce the internal resistance, measures such as improvement of additives, improvement of conductive aids and active materials, and application of carbon fine particles on the current collector in advance have been implemented. Further, the shape of the current collector has also been improved to make it as thin as possible as described above, and to increase the surface area by forming fine holes or the like in the foil. Similarly, in electric double layer capacitors, research and development are being carried out such as improvement of activated carbon and additives, and increase of contact area with current collectors.

As mentioned above, in secondary batteries such as electric double layer capacitors and lithium ion secondary batteries, which are power storage devices, large capacity, high output, and long life are used for electric vehicles, hybrid vehicles, and high power energy devices. Efforts are being made to reduce costs.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electrode of a power storage device capable of improving the charge / discharge speed of the power storage device and a method for manufacturing the electrode.

In order to solve the above problems, the present invention employs the following means.
In the method for manufacturing an electrode of a power storage device according to the first aspect of the present invention, short fibers of aluminum or copper, an adsorbent powder to which electrolyte ions are adsorbed during charging, or an active material powder to chemically react during charging / discharging, and a binder are used. The short fibers of aluminum or copper are collected by a slurry making step of making a liquid or gel-like slurry containing the slurry, a molding step of molding the slurry into a predetermined shape, and drying the slurry molded into the predetermined shape. It has a drying step of forming an electrode that functions as an electric body.

In this embodiment, when the slurry formed into a predetermined shape is dried, the short fibers of aluminum or copper are electrically connected to each other, and the non-woven fabric-like current collector or the dispersed short fibers are connected to each other by the short fibers. Is formed. Further, since the short fibers and the adsorbent powder or the active material powder are mixed in the slurry, when the slurry is dried, the adsorbent powder or the active material powder is formed in the gaps formed between the short fibers of the current collector. Enters. Therefore, the adsorbent powder or the active material powder is in direct contact with the short fibers or is arranged in the vicinity of the short fibers, and electrons are exchanged between the adsorbent powder or the active material powder and the short fibers of aluminum or copper. When done, the movement resistance can be reduced.

In the slurry preparation step of the above embodiment, the slurry containing the short fibers of aluminum or copper, the adsorbent powder or the active material powder, the binder, and carbon fibers having an average thickness of 0.5 μm or less is obtained. It is also possible to create it.
In this case, even when the adsorbent powder or the active material powder and the short fibers are not in direct contact with each other when the electrodes are formed, the adsorbent powder or the active material powder and the short fibers are electrically connected to each other via the carbon fibers. Connected to. Further, even when the adsorbent powder or the active material powder is in direct contact with the short fibers, the electric resistance between the adsorbent powder or the active material powder and the short fibers is further increased by the connection by the carbon fibers. It will be reduced.

Further, in the above embodiment, it is also possible to further perform pre-drying in which the slurry is dried until the binder is not completely cured before the molding step. In this case, since the slurry before the molding process can be easily molded, it is advantageous in improving the quality of the manufactured electrodes and reducing the manufacturing cost.

The electrode of the power storage device according to the second aspect of the present invention is formed between a current collector made of short fibers of aluminum or copper having an average length of 25 mm or less and the short fibers of aluminum or copper of the current collector. It is provided with an adsorbent powder that has entered the gap and is adsorbed by electrolyte ions during charging or an active material powder that chemically reacts during charging and discharging.

In this embodiment, since the adsorbent powder or the active material powder has entered the gap formed between the short fibers of the current collector, the adsorbent powder or the active material powder comes into direct contact with the short fibers or the staple fibers. It is arranged in the vicinity of the above, and when the transfer of electrons is performed between the adsorbent powder or the active material powder and the short fibers of each aluminum or copper, the movement resistance thereof can be reduced.

In the above embodiment, carbon fibers having an average thickness of 0.5 μm or less that have entered the gaps of the current collector may be further provided.
In this case, even when the adsorbent powder or the active material powder and the short fibers are not in direct contact with each other, the adsorbent powder or the active material powder and the short fibers are electrically connected via the carbon fibers. Further, even when the adsorbent powder or the active material powder is in direct contact with the short fibers, the electric resistance between the adsorbent powder or the active material powder and the short fibers is further increased by the connection by the carbon fibers. It will be reduced.

In the above embodiment, the collector has at least one portion where the two aluminum or copper staple fibers are in contact with each other so as to intersect, and the two aluminum or copper fibers at the intersecting portion. May bite into each other.
In this case, the movement resistance of electrons at the contact portion between the short fibers can be reduced, which is advantageous in reducing the resistance of electrons moving to the input / output terminals.
Further, in the above embodiment, it is preferable to use aluminum having a purity of 99.9% or more as the aluminum.

According to the present invention, the charge / discharge speed of the power storage device can be improved.

It is sectional drawing of the electrode which concerns on one Embodiment of this invention. It is a schematic diagram of the manufacturing method of the slurry of this embodiment. It is a schematic diagram of the method of molding the slurry of this embodiment into a predetermined shape. It is a schematic diagram of another method of molding the slurry of this embodiment into a predetermined shape. It is sectional drawing of the electrode which concerns on the 1st modification of this embodiment. It is sectional drawing of the electrode which concerns on the 2nd modification of this embodiment. It is sectional drawing of the coin type secondary battery using the electrode of this embodiment. It is sectional drawing of the conventional coin type secondary battery. It is sectional drawing of the electric double layer capacitor using the electrode of this embodiment.

An electrode according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, this electrode is in the form of a non-woven fabric made of short fibers A of aluminum or copper having an average wire diameter of 100 μm or less, or is a current collector 10 arranged so that the short fibers A are in contact with each other. The current collector 10 is provided with an active material powder 20 that is held by the binder B and chemically reacts during charging and discharging, and the current collector 10 is provided with a conductive auxiliary agent 30 held by the binder B, if necessary.

Note that FIG. 1 is a diagram for showing the configuration of the present embodiment in an easy-to-understand manner, and the sizes, thicknesses, lengths, etc. of the short fibers A, the active material powder 20, the conductive auxiliary agent 30, the carbon fiber CF, etc. are actually shown. Different from. Further, in FIG. 1, it is also possible to cause the current collector 10 to hold the adsorbent powder to which the electrolyte ion is adsorbed during charging instead of the active material powder 20.

[Molding of short aluminum fibers that serve as current collectors]
As an example, the aluminum or copper staple fiber A has an average length of 25 mm or less, preferably 20 mm or less, more preferably 15 mm or less, and an average wire diameter of 50 μm or less, preferably 25 μm or less. The short fibers A of aluminum or copper are formed by, for example, a chatter vibration cutting method in which a cutting tool is applied to a columnar member of aluminum or copper having a circular cross section, or a milling cutting method. It is also possible to mold aluminum or copper staple fibers having the wire diameter and length by other methods.

[Electrode molding]
First, a liquid or gel-like slurry S containing short fibers A of aluminum or copper, an active material powder 20 that chemically reacts during charging and discharging, a conductive auxiliary agent 30, and a binder B is prepared. The slurry S is prepared by kneading a mixture of short fibers A of aluminum or copper, active material powder 20, a conductive auxiliary agent 30, and a diluted binder B. Since the aluminum or copper staple fiber A has an average length of 25 mm or less, the aluminum or copper staple fiber A, the active material powder 20, and the conductive auxiliary agent 30 are likely to be mixed in the slurry S. When the average length of the staple fibers A is 15 mm or less, they tend to be more easily mixed.

Subsequently, pre-drying is performed to increase the viscosity of the slurry S. The pre-drying is to dry the binder B to a state where it is not completely cured, thereby facilitating the formation of the slurry S into a predetermined shape, and thus it can be omitted depending on the viscosity of the binder B.
Subsequently, as shown in FIG. 3, the slurry S is placed in the mold and the slurry S is pressurized. As a result, the slurry S is formed into a predetermined thickness or the like according to the size of the electrode. As shown in FIG. 4, it is also possible to pressurize the slurry S by passing the slurry S between the pair of rollers, thereby forming the slurry S into a predetermined thickness according to the size of the electrode. .. After adjusting the thickness of the slurry S with a mold or a roller, it is also possible to cut the slurry S and form it into a predetermined shape (size).

Subsequently, a drying step of drying the molded slurry S by vacuum drying or the like is performed. As a result, the binder B in the slurry S is cured, and the active material powder 20 and the conductive auxiliary agent 30 in the slurry S are held by the short fibers A of the current collector 10 by the binder B. Depending on the amount of the staple fibers A in the slurry S, after the staples S are dried, the staple fibers A are dispersed in the dried staples S and the staple fibers A arranged in the vicinity of each other are in direct contact with each other. Alternatively, the short fibers A arranged in the vicinity of each other are electrically connected to each other via the active material powder 20 and the conductive auxiliary agent 30, whereby the short fibers A dispersed in the slurry S cause the current collector 10 to be formed. It may be formed. Even in this case, at least a part of the active material powder 20 and the conductive auxiliary agent 30 in the slurry S is held by the staple fibers A.

It is also possible to perform a pressurizing step of pressurizing the current collector 10 after the drying step. As the pressurizing step, it is possible to perform a process of passing the current collector 10 between a pair of rollers, a process of sandwiching the current collector 10 between a pair of planes, a process of pressurizing the current collector 10 by a mold, and the like. ..

By using aluminum or copper, particularly preferably by using aluminum having a purity of 99.9% or more, and more preferably by using aluminum having a purity of 99.99% or more, after the pressurization and drying steps of FIGS. 3 and 4. By adjusting the pressing force when pressurizing the current collector 10, the two intersecting end fibers A bite into each other at the portion where the short fibers A are in contact with each other so as to intersect with each other. It is possible to transform it into. That is, the short fibers A are flattened at the contacting portion, so that the two intersecting end fibers A appear to bite into each other.

In this case, the movement resistance of electrons at the contact portion between the short fibers A can be reduced, which is advantageous in reducing the resistance of electrons moving to the input / output terminals.
It is also possible to prepare a slurry S containing an adsorbent powder to which electrolyte ions are adsorbed during charging instead of the slurry S containing the active material powder 20. In this case, the adsorbent powder is held in place of the active material powder 20 in the short fibers A of the current collector 10 after the drying step.

[Active substance powder]
The active material powder 20 may be one that can be held in the current collector 10 by a binder B or the like, or one that can be held in the binder B cured together with the current collector 10, and is preferably one having excellent cycle characteristics. Examples of the active material include lithium cobalt oxide (LiCoO ₂ ), iron phosphate-based active materials, and carbon materials such as graphite. It is possible to use known active materials used for the positive electrode and the negative electrode of the secondary battery.

[Adsorbent powder]
The adsorbent powder used in place of the active material powder 20 may be one that can be held in the current collector 10 by a binder B or the like, or one that can be held in the binder B cured together with the current collector 10. Those with excellent characteristics are preferable. Examples of the adsorbent powder include polyacene (PAS), polyaniline (PAN), activated carbon, carbon black, graphite, carbon nanotubes and the like. It is possible to use known substances used for the positive electrode and the negative electrode of the electric double layer capacitor.

It is preferable that the active substance powder 20 and the adsorbed substance powder are pulverized using a mortar, a ball mill, a vibrating ball mill, or the like to reduce the average particle size to a predetermined value or less. As a predetermined value, a value obtained by adding 10 μm to the average wire diameter of the short fibers A of the current collector 10 can be considered. For example, when the average wire diameter of the staple fiber A is 20 μm, the average particle size of the active material powder 20 and the adsorbent material powder is preferably 30 μm or less. As a result, the contact area between the short fibers A of the current collector 10 and the active material powder 20 or the adsorbent material powder increases, which can contribute to the improvement of the charge / discharge rate.

[binder]
As the binder B, a thermoplastic resin, a polysaccharide polymer material, or the like can be used. Examples of the material of the binder include a polyacrylic resin, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), and the like. .. It is possible to use a known binder used for an electrode of a secondary battery or an electric double layer capacitor.

[Conductive aid]
The conductive auxiliary agent 30 may be any material having conductivity, and is preferably a material that does not chemically change depending on the electrolyte or the solvent. Examples of the conductive auxiliary agent 30 include graphite and carbon black. It is possible to use a known conductive auxiliary agent used for an electrode of a secondary battery or an electric double layer capacitor.

The electrodes made as described above can be used as electrodes for storage devices such as electric double layer capacitors, secondary batteries, and hybrid capacitors including lithium ion capacitors. For example, it can be used for the positive electrode and the negative electrode of an electric double layer capacitor, and can be used for the positive electrode and the negative electrode of a lithium ion secondary battery as an example of a secondary battery, and is used for the positive electrode and the negative electrode of a lithium ion capacitor. It is possible. An example of its application will be described later.

The slurry S contains, in addition to the active material powder 20, the conductive auxiliary agent 30, and the binder B, a powder of carbon fiber CF having an average thickness of 0.5 μm or less, preferably 0.3 μm or less. It is also possible to use. In this case, as shown in FIG. 5, the carbon fiber CF is arranged in the gap formed in the current collector 10.

The carbon fiber CF comes into contact with the staple fiber A, the active material powder 20, the conductive auxiliary agent 30, and other carbon fiber CF. In this embodiment, carbon fiber CF having an average thickness of 0.1 to 0.2 μm and a length of about 20 to 200 μm is used. The resistivity of the carbon-based conductive auxiliary agent 30 is 0.1 to 0.3 Ω · cm, whereas the resistivity of the carbon fiber CF is, for example, 5 × 10 ^-5 Ω · cm.

For example, even when the active material powder 20 and the short fibers A are not in direct contact with each other, the active material powder 20 and the short fibers A are electrically connected via the carbon fiber CF. Further, even when the active material powder 20 and the short fibers A are in direct contact with each other, the electrical resistance between the active material powder 20 and the short fibers A is further reduced due to the connection by the carbon fiber CF. ..
As described above, the carbon fiber CF having good conductivity can reduce the resistance of electrons to move between the active material powder 20 and the staples A, and can reduce the resistance of electrons to move to the input / output terminals. It is advantageous.

It is also possible to manufacture an electrode using a slurry containing carbon fiber CF without containing the conductive auxiliary agent 30. Also in this case, as shown in FIG. 6, the carbon fiber CF is arranged in the gap formed in the current collector 10, and the configuration reduces the electric resistance between the active material powder 20 and the short fibers A. It is advantageous on. 5 and 6 are views for showing the configuration of the present embodiment in an easy-to-understand manner, and are the sizes, thicknesses, and lengths of the staple fibers A, the active material powder 20, the conductive auxiliary agent 30, the carbon fiber CF, and the like. May differ from the actual one.
In order to efficiently reduce the electrical resistance, the average length of the carbon fiber CF is preferably half or more of the average particle size of the active material powder 20 and the adsorbent material powder, and is 2 of the average particle size. It is more preferable that it is / 3 or more.

[Application to coin-type secondary batteries]
FIG. 7 shows an example of a coin-type secondary battery using the electrodes of the present embodiment. This coin-type secondary battery includes a case (exterior can) 100 having a case main body 102 and a lid 101, and a power storage unit housed in the case 100. The power storage unit includes an electrode using the short fiber A made of aluminum of the present embodiment as the positive electrode 110. Further, it has a negative electrode 120 that opposes the positive electrode 110 and a separator 130 that is arranged between the positive electrode 110 and the negative electrode 120. The positive electrode 110 comes into surface contact with the case body 102, and the negative electrode 120 comes into surface contact with the lid 101, whereby the lid 101 and the case body 102 function as input / output terminals for the positive electrode 110 and the negative electrode 120.

In this case, the active material powder 20 for the positive electrode is held in the current collector 10 used for the positive electrode 110. Further, the negative electrode 120 may have a structure and material of a known negative electrode of a secondary battery, and in the case of a lithium ion secondary battery, a carbon material such as graphite is used as an active material, and copper is used as a current collector. Foil is used. The separator 130 may be any as long as it electrically insulates the positive electrode 110 and the negative electrode 120, has ion permeability, and has resistance to oxidation / reduction at the contact surface between the positive electrode 110 and the negative electrode 120. For example, porous polymers and inorganic materials, organic and inorganic hybrid materials, glass fibers and the like can be used. It is possible to use a known separator used for a secondary battery.

The case 100 containing the power storage unit is filled with an electrolytic solution. A lithium salt, a potassium salt, a sodium salt, a magnesium salt or the like can be used as the electrolyte of the electrolytic solution, and in the case of a lithium ion secondary battery, the lithium salt is used. A non-aqueous solvent is used as the solvent in which the electrolyte is dissolved, and ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, carbonic acid ester and the like can be used as the non-aqueous solvent. It is possible to use known electrolytes and solvents used in secondary batteries. When charging and discharging are performed, a chemical reaction occurs in which ions such as lithium ions are released from the active material powder 20 of the positive electrode 110 into the electrolytic solution, and a chemical reaction in which ions such as lithium ions are taken into the active material powder 20 occurs. ..

In the coin-type secondary battery configured as described above, one surface of the current collector 10 used for the positive electrode 110 in the thickness direction comes into contact with the case body 102. Further, the current collector 10 used for the positive electrode 110 is filled with the active material powder 20 in the entire range from one surface to the other surface in the thickness direction, and many active material powders 20 collect electricity. It is in contact with the staple fibers A of the body 10. Therefore, the distance between the staple fiber A carrying electrons to the input / output terminal and the active material powder 20 becomes short, which is advantageous in improving the charge / discharge speed.

Further, the active material powder 20 and the short fibers A are in direct contact with each other, or the active material powder 20 and the short fibers A are arranged in close proximity to each other and are electrically connected via the conductive auxiliary agent 30 or the like. Therefore, when electrons are exchanged between the active material powder 20 and the staple fibers A, the resistance at which the electrons move to the input / output terminals provided at the ends of the current collector 10 or the like can be reduced. can.

An example of a conventional coin-type secondary battery is shown in FIG. This coin-type secondary battery includes a positive electrode 140 having an aluminum foil current collector 141 and an electrode layer 142 coated on one surface of the current collector 141 in the thickness direction. The electrode layer 142 contains an active material powder, a conductive auxiliary agent, a binder and the like. Since the space of the coin-type secondary battery is limited, the amount of the active material powder in the conventional coin-type secondary battery is limited by the thickness of the current collector 141. Further, the electrons of the active material powder arranged on the separator 130 side move to the current collector 141 via the active material powder and the conductive auxiliary agent arranged between the current collector 141 and the current collector 141, so that the charge / discharge speed can be adjusted. It is not preferable for improvement.

In the coin-type secondary battery, it is also possible to use the electrode structure of the present embodiment, particularly an electrode using short fibers A made of copper, for the negative electrode 120. In this case, the current collector of this electrode is the current collector 10, a carbon material is used as the active material powder 20, and lithium titanate, titanium oxide, tungsten oxide, tin oxide, or the like is used depending on the type of battery. It may be possible.

[Application to laminated secondary batteries]
In the case of a secondary battery in which a storage unit composed of a positive electrode, a negative electrode and a separator is laminated in a plurality of layers, the electrode structure using the short fiber A of aluminum or copper of the present embodiment is applied only to the positive electrode as in the case of the coin type secondary battery. It can be used only for the negative electrode and for both the positive electrode and the negative electrode.

[Application to electric double layer capacitors]
FIG. 9 shows an example of an electric double layer capacitor using the electrodes of the present embodiment. This electric double layer capacitor includes, for example, a container 200 and a storage unit housed in the container 200. The power storage unit includes an electrode using the aluminum staple fiber A of the present embodiment as the positive electrode 210. Further, it has a negative electrode 220 that opposes the positive electrode 210 and a separator 230 that is arranged between the positive electrode 210 and the negative electrode 220. A positive electrode input / output terminal 210a is connected to the positive electrode 210, a negative electrode input / output terminal 220a is similarly connected to the negative electrode 220, and each input / output terminal extends to the outside of the container 200.

In this case, the current collector 10 used for the positive electrode 210 holds the adsorbent powder. Further, the negative electrode 220 may have a structure and material of a negative electrode of a known electric double layer capacitor, and is applied to, for example, a current collector 221 made of aluminum foil and one surface of the current collector in the thickness direction. It has an electrode layer 222 and. The electrode layer 222 contains adsorbent powder, a conductive auxiliary agent, a binder and the like.

The separator 230 may be any as long as it electrically insulates the positive electrode 210 and the negative electrode 220, has ion permeability, and has resistance to oxidation / reduction at the contact surface between the positive electrode 210 and the negative electrode 220. For example, porous polymers and inorganic materials, organic and inorganic hybrid materials, glass fibers and the like can be used. It is possible to use a known separator used for an electric double layer capacitor.

The container 200 containing the power storage unit is filled with an electrolytic solution. The electrolytic solution contains a non-aqueous solvent and an electrolyte. The electrolyte and the non-aqueous solvent may be any known substance used for the electric double layer capacitor. For example, ammonium salt, phosphonium salt and the like can be used as the electrolyte, and for example, cyclic carbonate ester, chain carbonate ester, cyclic ester, chain ester, cyclic ether, chain ether, nitriles, sulfur-containing compound and the like can be used as the non-aqueous solvent. can.

In this electric double layer capacitor, one end of the current collector 10 used for the positive electrode 210 is connected to the positive electrode input / output terminal 210a. Further, the current collector 10 used for the positive electrode 210 is filled with adsorbent powder in the entire range from one surface to the other surface in the thickness direction, and many adsorbent powders are contained in the current collector 10. Is in contact with the short fibers A of. Therefore, the distance between the staple fiber A carrying electrons to the positive electrode input / output terminal 210a and the adsorbent powder becomes short, which is advantageous in improving the charge / discharge rate. Since the structure of the conventional positive electrode is the same as that of the negative electrode 220, it is easier to understand the above advantages as compared with the negative electrode 220.
In the electric double layer capacitor, it is also possible to use the electrode structure using the aluminum staple fibers A of the present embodiment for the negative electrode 220. It is also possible to use the electrode structure using the copper staple fibers A of the present embodiment for the positive electrode 210 and the negative electrode 220.

According to the present embodiment, as described above, it is possible to form an electrode of a power storage device in which the active material powder 20 and the adsorbent powder are arranged in the vicinity of the high-purity aluminum staple fiber A and the copper staple fiber A. be. This makes it possible to manufacture a power storage device having a higher capacity, less deformation resistance, and excellent charge / discharge performance.

Also, for example, in the production of aluminum foil used for ordinary capacitors and secondary batteries, a very large square pillar aluminum ingot called a slab is made, cut, heated and rolled many times, and then further. Manufactured with surface treatment. This requires a great deal of energy and cost. On the other hand, the aluminum or copper staple fibers A used in the present embodiment can be manufactured by chatter vibration cutting or the like. Further, when the current collector 10 holding the adsorbent powder, the active material powder 20, the conductive auxiliary agent 30, and the like is rolled to form a foil, the pressing pressure can be reduced. Therefore, it is possible to easily and inexpensively manufacture a current collector foil and a positive electrode foil without requiring a large-scale equipment.

As described above, according to the present embodiment, when the slurry formed into a predetermined shape is dried, the aluminum or copper staple fibers A are electrically connected to each other, and the aluminum or copper staple fibers A form the current collector 10. It is formed. Further, since the short fibers A of aluminum or copper and the adsorbent powder or the active material powder 20 are mixed in the slurry S, when the slurry S is dried, it is formed between the short fibers A of the current collector 10. Adsorbent powder or active material powder 20 enters the gap. Therefore, the adsorbent powder or the active material powder 20 is in direct contact with the short fiber A or is arranged in the vicinity of the short fiber A, and electrons are exchanged between the adsorbent material powder or the active material powder 20 and the short fiber A. When this is done, the movement resistance can be reduced.

Further, since the carbon fiber CF is mixed in the slurry S, even when the adsorbent powder or the active material powder 20 and the short fiber A are not in direct contact with each other when the electrode is formed, the adsorbent powder or the active material The powder 20 and the short fibers A are electrically connected via the carbon fiber CF. Further, even when the adsorbent powder or the active material powder 20 and the short fiber A are in direct contact with each other, the adsorbent material powder or the active material powder 20 and the short fiber A can be separated from each other by the connection by the carbon fiber CF. The electrical resistance is further reduced.

Further, an electrode having a non-woven fabric-like current collector made of short fibers A or a current collector in which dispersed short fibers A are connected to each other bends more easily even with a small force than those using aluminum foil or the like as a current collector. .. Therefore, when the installation space of the electrode is limited, it is possible to facilitate the installation, and even if the electrode is provided at a position where a slight deformation is applied during use, the reaction force generated from the electrode becomes small. This can be expected to improve the life of the equipment.

10 Collector 20 Active material powder 30 Conductive aid A Aluminum or copper staple fiber B Binder S Slurry CF Carbon fiber

Claims (11)

Short fibers of aluminum or copper, adsorbent powder that adsorbs electrolyte ions during charging or active material powder that chemically reacts during charging and discharging, conductive auxiliary agent, binder, and carbon fiber having an average thickness of 0.5 μm or less. A slurry preparation step for producing a liquid or gel-like slurry containing the above, wherein the average length of the carbon fibers is 200 μm or less, except for carbon fibers having an average length of 30 μm or less. When,
A molding process for molding the slurry into a predetermined shape, and
A method for manufacturing an electrode of a power storage device, which comprises a drying step of forming an electrode in which the aluminum or copper staple fibers function as a current collector by drying the slurry formed into the predetermined shape.
A method for manufacturing an electrode of a power storage device, excluding short fibers having an average length of 25 mm or less, but having an average length of 1 mm or less. The method for manufacturing an electrode of a power storage device according to claim 1, wherein the staple fiber has an average wire diameter of 50 μm or less, except for the staple fiber having an average wire diameter of 10 μm or less. The method for manufacturing an electrode of a power storage device according to claim 1 or 2, wherein the short fiber is formed by applying a cutting tool to an aluminum or copper member. Short fibers of aluminum or copper, adsorbent powder that adsorbs electrolyte ions during charging or active material powder that chemically reacts during charging and discharging, conductive aid, binder, and carbon fiber having an average thickness of 0.5 μm or less. A slurry making process for making a liquid or gel-like slurry containing and
A molding process for molding the slurry into a predetermined shape, and
A method for manufacturing an electrode of a power storage device, which comprises a drying step of forming an electrode in which the aluminum or copper staple fibers function as a current collector by drying the slurry formed into the predetermined shape.
The average length of the staple fibers is 25 mm or less, and the staple fibers have an average length of 25 mm or less.
A method for manufacturing an electrode of a power storage device, wherein the staple fiber is formed by applying a cutting tool to an aluminum or copper member. The method for manufacturing an electrode according to any one of claims 1 to 4 , wherein aluminum having a purity of 99.9% or more is used as the aluminum. The method for producing an electrode according to any one of claims 1 to 5 , further comprising a pre-drying step of drying the slurry until the binder is not completely cured before the molding step. Short fibers of aluminum or copper, adsorbent powder that adsorbs electrolyte ions during charging or active material powder that chemically reacts during charging and discharging, conductive aid, binder, and carbon fiber having an average thickness of 0.5 μm or less. A liquid or gel-like slurry containing and, which is formed into a predetermined shape for an electrode of a power storage device.
The carbon fiber having an average length of 200 μm or less, except for the carbon fiber having an average length of 30 μm or less, is used.
A slurry for electrodes of a power storage device, excluding short fibers having an average length of 25 mm or less, but having an average length of 1 mm or less. A current collector made of aluminum or copper staple fibers excluding short fibers having an average length of 25 mm or less but an average length of 1 mm or less,
Adsorbent powder or active material powder that chemically reacts during charge / discharge , and an average An electrode of a power storage device including carbon fibers having a thickness of 0.5 μm or less. The electrode according to claim 8 , wherein the aluminum or copper staple fibers of the current collector are bent and present. The electrode according to claim 8 or 9 , wherein the aluminum has a purity of 99.9% or more. A slurry making step of making a liquid or gel-like slurry containing short fibers of aluminum or copper, an adsorbent powder to which electrolyte ions are adsorbed during charging, and a binder.
A molding process for molding the slurry into a predetermined shape, and
A method for manufacturing an electrode of a capacitor, which comprises a drying step of forming an electrode in which the aluminum or copper staple fibers function as a current collector by drying the slurry formed into the predetermined shape.
A method for manufacturing a capacitor electrode, excluding short fibers having an average length of 25 mm or less, but having an average length of 1 mm or less.

Images