WO2011139174A1

WO2011139174A1 - Double-layer capacitor or ultracapacitor device

Info

Publication number: WO2011139174A1
Application number: PCT/RU2010/000221
Authority: WO
Inventors: Андрей Яковлевич КОГАН
Original assignee: Kogan Andrey Yakovlevich
Priority date: 2010-05-04
Filing date: 2010-05-04
Publication date: 2011-11-10

Abstract

The invention relates to a device of electrodes in double-layer capacitors with a high specific power. If only one of the electrodes of the capacitor is manufactured from an activated carbon fiber which is coated with a thin porous polymeric film. Therefore, each thread comprises an active material with a developed surface (10) and a separator (11), which ensures the simplicity in manufacture of the capacitors. For high-power capacitors, in addition to the carbon fiber a thin metal wire (9) is incorporated in the thread in order to reduce the resistance. Alternating the connection of the threads (8) to one electrical lead (6) and the other electrical lead (7) ensures a large surface area of contact between the electrodes and a high specific power. The use of the proposed design which combines an electrode mass, a separator and an electrical lead in one thread makes it possible to manufacture inexpensive flat, flexible double-layer capacitors, capacitors with a high capacitance for hybrid automobiles and capacitors with an extra-high capacitance for power supply systems, both with a symmetrical and with an asymmetrical design.

Description

The device is a double layer capacitor or ultracapacitor.

The invention relates to the production of electrical devices, and more particularly to the design and materials of electrodes of ultracapacitors or otherwise double layer capacitors.

Double layer capacitors are also known, also called ultracapacitors, ionistors or supercapacitors. Such devices are capable of storing more energy per unit volume than traditional capacitors, delivering more power than chemical batteries, and withstanding a greater number of charge-discharge cycles. Ultra capacitors with a capacity of thousands of Farads are used for backup power supply of electrical appliances, in starting equipment

automobile and locomotive engines, as energy storage in hybrid cars.

These devices achieve high capacitance due to the large surface of the electrodes used. Conventional capacitors, as a rule, consist of two metal plate-electrodes separated by a dielectric. Since the capacitance is proportional to the area of the electrodes, large capacitors must have a large plate area. The ultracapacitor electrode material used for advanced microstructure and high surface area of the order of 1 LLC m ² / g, for example, activated carbon.

Known ultracapacitors, consisting of electrodes with a developed surface, an electrolyte, a separator, a housing and current collectors brought to the surface of the housing.

The classic design of the ultracapacitor, for example, in the patent US6212062 (B1) "Sealed ultracapacitor" in figure 1. The ultracapacitor includes a dielectric housing (1), a pair of carbon electrodes of activated carbon (2) or other material having a large specific surface area of the porous separator ( 3), an electrolyte (4), a pair of conductive layers that serve as current collectors (5).

The ultracapacitor works as follows. A double electric layer is formed on the surface of the electrodes, which prevents leakage.

DC through capacitor. The larger the surface of the electrodes, the greater the capacitance of the capacitor. Therefore, materials with a specific surface of several hundred square meters per gram are usually used for the manufacture of electrodes. The separator prevents direct electrical contact between the electrodes, so the current provides the movement of ions in the electrolyte. Jonah pass through the through pores in the separator. The more porous the separator and the larger its surface, the lower the internal resistance of the capacitor and the more power it can give. The maximum voltage allowed on a double electric layer without noticeable destruction of the electrolyte and electrodes depends on the chemical nature of the electrolyte. The mobility of electrolyte ions affects the internal resistance of a supercapacitor. As a rule, an improvement in one of the electrolyte parameters leads to a deterioration of the other. Therefore, the design solution of the electrodes and the separator, which allows to reduce the internal

the resistance of the ultracapacitor, lead to the possibility of increasing the specific energy stored by the capacitor. An example of such a solution is the patent: “CO-EXTRUSION METHOD OF FABRICATING ELECTRODE STRUCTURES IN HONEYCOMB SUBSTRATES AND ULTRACAPACITOR FORMED THEREBY))

WO2007142915. Each electrode is made in the form of many rectangular or square cells, and the cells occupied by one and the other electrode alternate in a checkerboard pattern. This scheme allows you to increase the surface of the separator by about 4 (N) ¹⁷² , where N is the number of cells. The disadvantage of the proposed solution is the complexity of the design, and this complexity increases with decreasing cell size. Probably the minimum reasonable cell sizes should not be less than 1 mm. Another disadvantage is that in such a design, the separator is made only of solid materials such as silicon carbide. This limitation affects the specific characteristics of the separator.

Also known are devices in which electrodes are made from

conductive fibrous materials with a large specific surface area. For example, in the book “Carbon Fiber” by V.Ya. Varshavsky published in 2007, UDC 547 BBK 35.73 In 188, on pages 414-415, the unit cell of a double layer capacitor is described. As electrodes were used

modified carbon fibers from isotropic pitch having a developed surface, a separator made of perforated polypropylene film and two current collectors made of hydrophobized fabric based on carbon fibers were used. The cell is enclosed in a sealed volume of polyethylene. Sulfuric acid was used as an electrolyte. As in the classical design, the cell volume is divided in the middle by a separator, and each of the two electrodes is localized in one half-space. The disadvantage of this design is its unsuitability for easy scaling. As the size of the cell increases, PT / U2010 / 000221 influence of internal resistance. The internal resistance of the cell depends on the average distance between the electrodes, the quality of the separator, its area, and the mobility of the electrolyte ions. With a proportional increase in all elements of the cell by L times, its capacitance increases in L, the area of the separator increases in L, and the average distance between the electrodes increases in L.

characteristics such as power density and frequency at which the capacitor can operate efficiently are degraded by approximately L ² times. This design flaw leads to the fact that electrolytes, which can increase the voltage on the cell, but with lower ion mobility, are often used in smaller capacitors.

The proposed design is devoid of this drawback. The material of the electrodes consists of electrically conductive filaments with a developed surface, each of which, as in a stocking, is enclosed in a porous film or mesh that acts as a separator. Those. this coating freely passes electrolyte ions and

direct contact and transfer of electrons from one filament to another even when the filaments are pressed tightly against each other. The entire design of the ultracapacitor is transferred to the micro level. Two such filaments, placed in an electrolyte and pressed against each other, are an ultracapacitor in miniature. The number of threads can be any, it is important that the threads connected to different current collectors are located in close proximity to each other, alternating. For example, they can be arranged in layers with an offset of one layer relative to the other by half a step. They can be woven into a braid, woven in the form of a fabric, or woven according to the principle of conductors in a twisted pair cable. Figure 2 shows how to weave an ultracapacitor from threads enclosed in a porous shell. Two flexible current collectors (6) and (7) are connected each with its own set of threads from

activated carbon fiber enclosed in a porous membrane (8). Such a fabric provides an opportunity for many design solutions.

ultracapacitors. For example, you can wet it with electrolyte and solder it between two layers of elastic plastic. Get a thin capacitor in a flexible case. You can twist it into a tight roll and place it in a cylindrical body filled with electrolyte. Electrodes occupy the same capacitance with

electrolyte, interpenetrating each other, the contact surface is larger, and the internal resistance is less than traditional

ultracapacitors. In contrast to the prototype, with an increase in the mass of such The “combined” electrode, the specific power and effective frequency change only slightly, because the ion transport distance and the specific area of the separator remains unchanged for any unit cell size.

A key element in the design is the thread constituting the electrodes. Activated carbon fiber can be taken as a basis, due to which its specific surface area increases to 300-1500 m ² / g. The fiber thickness can be in the range from 1 μm to 100 μm, and for capacitors with a capacity of more than 1000 F to 1 mm. An ideal thread should be considered, the surface layers of which have a developed porous structure, and the core has good electrical conductivity. Such a structure can be obtained in various ways.

For example, a thread may consist of many fibers twisted like

ordinary thread, and part of the fibers may be pre

activated, and part have a denser structure and a larger

electrical conductivity than activated carbon fiber. The thread is covered with a porous separator film.

It is possible, as shown in figure 3, to use a thin metal wire (9) as a current collector, around which fibers of activated carbon fiber (10) are wrapped, acting as an electrode material, this combined thread is enclosed in a stocking of a porous insulating material - separator (11) . You can replace the fibers with activated carbon or graphene powder deposited on a metal wire.

Or you can use hollow polymer fibers of relatively large diameter from 100 microns to 5 mm, a metal wire with a diameter several times smaller than the inner diameter of the hollow fiber is inserted into the inner channel of each of them, and the remaining space inside the fiber is filled with fine powder of activated carbon.

Finally, it is possible to select an activation mode so that the outer surface of the carbon fiber undergoes a greater structural change than the core. The simplest option is activated carbon monofilament.

The surface of the thread consists of a film of a porous insulating material, for example, a polymer, with pores whose characteristic size is less than the radius of the fiber, but sufficient for the passage of ions used in the electrolytic capacitor. Such a film can be obtained by one of the known methods, for example, by spontaneous gelation, or by leaching. Best result possible achieved using the Rebinder effect, since in this case it is possible to obtain films with pores elongated along the threads, which is the best result. Here is an example of one of the options for constructive solutions to the above schemes. The material for the electrodes of the coins is carbon modified fiber with a filament diameter of 5 μm, enclosed in a shell of porous lavsan with pores of about 1 μm. A significant drawback of this material is that lavsan is not acid resistant, therefore, sulfuric acid should not be used as an electrolyte. Fibers of equal length 140 mm are laid in layers, with even layers

are shifted along the fiber by 15 mm in one direction, and odd in the other.

The resulting bundle with a diameter of about 40 mm is enclosed in a heat-shrinkable tube and crimped. The tube is filled with electrolyte and the ends of the tube are closed

sealant. The remaining ends of the threads on both sides of the tube are freed from the insulating film and connected to the current collectors. The resulting capacitor has an average distance between the electrodes of about 10 μm, a separator area of about 20 m ² , includes about 40 g of activated carbon fiber with a specific surface area of 350 m / g. A similar capacitor design can

Scale by changing any of the following sizes: the diameter of the fiber and threads, the length of the fiber segments, the diameter of the tow and others.

Another example of a structural solution is a capacitor having a different design of electrodes. The first electrode consists of conductive threads made on the basis of hollow polymer fibers, as described above. A bundle of such threads is enclosed in a closed volume, with all metal wires connected to a common current collector. The second electrode also consists of activated carbon powder, or other electrode material. This electrode fills the space between the hollow fibers. To improve the current collector from the second electrode, metallic threads or metal foil are introduced into it,

connected to the second current collector. Alternatively, the second electrode can be made in the form of a thin layer of activated carbon powder deposited on the surface of the hollow fiber and fixed, for better current collector, deposited on top of the powder with a metal film.

Claims

Claim.

1. The device is a double layer capacitor or ultracapacitor, including an electrolyte, current collectors, a separator and an electrode mass containing material with a high specific surface area of more than 50 m ² / g, characterized in that at least one of the electrodes is made of conductive threads coated with a porous a dielectric film acting as a separator.

2. The device of the electric ultracapacitor according to claim 1., In which both

the electrodes are made of conductive threads coated with a porous dielectric film, all the threads are bundled, or woven into a bundle, or woven into fabric, or stacked in rows, and the threads connected to different current collectors alternate.