JP2000502209A - Double layer capacitor having porous carbon electrode and method for manufacturing these electrodes - Google Patents

Abstract

(57) Abstract: At least two electrodes (4, 5) consisting essentially of porous carbon, the electrodes being substantially saturated with an electrolyte and separated by a porous separator (6). Heavy electric layer capacitor. The capacitor has a porous structure of the electrode (4,5) having a carbon content of more than 95% by mass and a pore volume of more than 55% of the electrode material volume (a certain part of the pores has a size of less than 10 nm). Made from materials that have

Description

DETAILED DESCRIPTION OF THE INVENTION                 A double-layer capacitor having a porous carbon electrode; and                 Manufacturing method of these electrodes   The present invention relates to an electrical device, in particular a storage structure for electricity, which comprises, for example, a personal computer. For radio units for computer, video and other equipment, radio electric Can be used as a short-time or reverse power source for the current for the device.   Further, the present invention relates to a method for producing a porous carbon material and a capacitor electrode material.   One of the main directions in the development of high efficiency capacitors with dual electrical layers is optimal pore size Novel electrode carbon material with a combination of properties such as size, mechanical strength and high chemical purity Is to make a fee.   As conventionally known, a separator placed in an airtight frame Thus, there is a capacitor having a double electrical layer containing bipolar electrodes separated (eg, For example, Japanese Patent Application No. 3-622296). The electrode is activated carbon and a binder (carbon Rack and ceramic powder). The electrode material is porous With 25 F / cm^ThreeThe following specific electrical capacitance results.   The disadvantages of such capacitors are as follows:   Significant leakage current due to large (3-8%) ash content in electrical materials;   -Changes in the microporous properties of the electrode material in the method of manufacturing the electrode and capacitor assembly; Change of capacitor characteristics due to   -The mechanical strength of the electrode material is low (this can occur under conditions of high mechanical stress, e.g. vibration); Limiting the use of these capacitors in moving structures).   In addition, as is conventionally known, includes a stainless steel frame, The frame includes a bottom and lid joined by washers, which creates an airtight container. Some capacitors have a double electrical layer. The frame is saturated with electrolyte and A bipolar electrode separated by a porous separator is provided. Electrode is active Charcoal (80% by mass) and binder (ash (10% by mass) and polytetrafluoroethylene (10% by weight). The material in the form of a paste is It is applied to the conductive underlayer, then rolled and dried. From the generated sheet product An electrode of a defined size is cut.   Such capacitors can operate over a wide temperature range. Electrode material Is 20-25F / cm^ThreeGives a specific electrical capacitance within the limits of But Furthermore, these capacitors have all the disadvantages mentioned above.   The object of the present invention is to increase the electric capacitance of the capacitor, It is to simultaneously obtain a reduction in value fluctuation and a reduction in leakage current. Furthermore, the present invention The purpose is to obtain an increase in electrode strength and mechanical stability. This is, for example, Extends the area of use of capacitors in structures that operate under fire or vibration conditions right. In order to achieve this technical result, a core with a double electrical layer in an airtight frame The capacitor has at least two polarized electrodes of porous carbon installed in the frame. 95% pure, separated by a separator having ion conductivity Structures made from materials having a carbon content of greater than or equal to, preferably greater than or equal to 99% by mass Having an electrode of the form The material preferably has total pores in the range of 55-80% of the electrode volume Pore preferably having a volume and having a nanopore size smaller than 10 nm Is preferably 35-50% of the electrode volume. This enables high electric capacity You can get sitance.   According to a preferred embodiment, these electrode properties are specific to the metal carbide composite. It can be obtained by various chemical heat treatments. After such treatment, the electrodes are separated from the transport channels / pores. Substantially pure carbon with branching and small amounts of impurities (less than 5% by weight, preferably Less than 1% by mass). These electrodes have high electrode mechanical strength (90 kg / cm^Two Above compressive strength). Material produces mechanical stiffness and strength , A solid network of carbon connected throughout the structure, and the overall pore volume Of coarse electrolyte transport channels / pores and nanosites Consisting of a combination of fine pores. Stability of the electrode dimensions and its pores, The stability of the air quality is also important. Therefore the height and diameter from the intermediate product to the finished electrode The reduction in value is less than 0.05%, which is a practical capacitor capacity in the range of ± 15%. Allows very limited variation of electrode specific electrical capacitance that causes pacitance I do. On the other hand, conventional capacitors have +80 to -20% electrical capacitance tolerance Having.   Novel electrode compared to previous technical solutions with only low impurity content of electrode material And almost 30% specific electric capacitance and practical capacitor capacitance And a 5-10 fold reduction in leakage current. In addition, high electrode strength is vibration, Enables use in capacitors for equipment operating under shock and other mechanical stresses You.   The present invention will be described in more detail with reference to the illustrated embodiments and the accompanying drawings. Would. FIG. 1 gives a depiction (side view) of the entire capacitor, and FIG. A plot of voltage versus discharge time is provided.   Capacitors with double electrical layers have a bottom 1 and a lid 2 joined to a dielectric washer 3 Includes an airtight frame containing. Electrodes 4 and 5 are placed inside the frame You. The electrodes are saturated (impregnated) with an electrolyte and separated by a porous separator 6 I have. The opposite sides 4 ', 5' of the double electrode layer are in contact with the bottom 1 and the lid 2, respectively. You. To make capacitor assembly easier, elastic washers surrounding the electrodes There is Shah 7.   For confirmation of the technical results obtained, 12 carbon electrodes (diameter 19.5 mm, high 1.0 mm) and six button capacitors (diameter 24.5 mm, height 2.2) mm). Porous polypropylene with ion conductivity as separator And an aqueous solution of alkali and KOH was used as an electrolyte. Capacitor The nominal electrical capacitance was 20F and the voltage was 1.0 volt.   Investigate the physical and mechanical properties of the electrode materials and determine the power source and Operates under practical conditions as an electronic memory unit for the Sonal computer The capacitors were tested for reliability and potential for Trial about reliability The experiment was performed at a voltage of 0.9 ± 0.1 V and at a temperature of + 70 ± 5 ° C. The test time is 500 hours.   Test results of physical, chemical and mechanical properties of electrode materials and results of capacitor test The results are given by the graphs in Tables 1 and 2 and FIG.   The analysis of the results of the electrode test (Table 1) shows the pore volume (electrode volume) of size less than 10 nm. Average 43%) is about 2% of the parameters of carbon electrodes manufactured by the prior art. It shows that it is twice. The compressive strength increased more than three times. Specific electric capacitance (Average 34.5F / cm^Three) Is the specific capacitance of a known carbon material (25 F / cm^ThreeThe following).   The results of the reliability test (Table 2) show that the nominal capacitor Only shown (± 5.3%). It has a stable branch structure, High mechanical strength of carbon electrodes maintaining geometric electrode and electrolyte parameters Means   After the test, the capacity loss was 5.7% (average) and the increase in internal resistance was 18% (average). ), Which satisfies high performance requirements.   The results of the capacitor test (Fig. 2) show that the performance of the capacitor 198 hours at 100 kohm, 32 hours at 50 kohm load, 3 hours at 20 kohm load, negative It indicates that the load is 0.5 kohm for 2 hours. These data are Actual discharge of capacitors operating under loads of various devices that can be used as power sources It is a copy of.   According to a preferred embodiment, the electrodes are provided as silicon carbide powder and binder. Carbon black, phenol formaldehyde resin and 5 or 100 g of silicon carbide or ethyl alcohol mixture Produced from pyrocarbon in an amount of -50 g:          Carbon black 30-50          Phenol formaldehyde resin 5-10          Ethylated alcohol 40-60 After molding, the blank is saturated with liquid silicon at a temperature of 1450-1700 ° C4 Is done. The thermochemical treatment with chlorine is performed at a temperature of 900-1100 ° C.   The method is described below:   A blank of a predetermined shape is formed from the silicon carbide powder and the binder. Success Silicon carbide powder in the form is 5-50g per 100g of silicon carbide Suspension (the composition (% by mass) is carbon black 30-50, phenol Mixed with formaldehyde resin 5-10, ethylated alcohol 40-60) . The blank is formed by loading it. Next, at 150 ° C. to cure the resin Is performed. As an alternative added to silicon carbide powder Or a pyrocarbon binder introduced by heat treatment in a natural gas stream is used You.   After being formed by this method or another forming technique, the blank is placed in a vacuum furnace. Where saturation is achieved by liquid silicon at a temperature of 1450-1700 ° C. under vacuum. Done. During this process, the formation of the second silicon carbide and the liquid silicon and carbon (Carbon black or pyrocarbon) chemical interaction takes place. This second Silicon carbide forms a continuous structure over the entire volume of the blank, Silicon carbide particles to form residual pores filled with silicon metal. To form a solid silicon carbon body. At temperatures below 1450 ° C, silicon No id formation reaction takes place and the purpose of the method is not achieved. Silicon is 1700 ° C or less At the above temperature starts to evaporate in the vacuum furnace. Thus, free of second silicon carbide Nonporous bra containing silicon carbide particles bonded by a structure of silicon Link is obtained. The blank is then heat treated with chlorine at a temperature of 900-1100 ° C. Is managed. During chlorination, free silicon metal is removed from the blank in the form of gaseous silicon chloride. Is removed, thus forming the required volume of transported microporous channels / pores. Further In addition, as a result of silicon carbide chlorination, Element is formed.   The resulting solid carbon network transport channel / pore and nanopore combination is extremely Important. Because it is the great benefit created by the nanopore wall This is because it facilitates access of the electrolyte to the usable internal electrode surface. Continuous Carbon networks also provide low internal electrical resistance.   The function of the capacitor according to the invention will be clear from the above description.   The capacitor according to the present invention is compared with the prior art described in the introductory part of the description. It is advantageous.   The invention has been described with reference to the illustrated embodiments. However, other examples and It is understood that minor modifications are possible without departing from the inventive concept. right. For example, two or more electrodes may be provided in a capacitor.   Furthermore, a solid carbon with transport channels / pores and nanopores that produces the above advantages Material can also be manufactured by other methods that give a network structure of . The technology consists of metal carbides, organic binders and, for example, in the form of carbon black. Produces compacts containing carbon as a pyrolysis product, followed by thermochemical removal of metals To form a solid carbon structure containing the desired transport channels / pores and nanopores .   A specific example is an aluminum cover that significantly reduces the reaction temperature required for the first manufacturing process. It is also possible to use an aluminum and an aluminum metal. IV of Ti and periodic systems So-called cubic metal carbides based on other metals of the group V, VI or VI may also be used. In that case, gaseous metal halides (eg, fluorides and chlorides) are formed.

[Procedure for Amendment] Article 184-8, Paragraph 1 of the Patent Act [Date of Submission] November 27, 1997 (1997.11.27) [Content of Amendment] Description Double-layer capacitors having porous carbon electrodes and The present invention includes at least two electrodes substantially composed of porous carbon, wherein the electrodes are saturated with an electrolyte and separated by a porous separator having ion conductivity, and the solid carbon is connected to the electrodes. The present invention relates to a double-layer capacitor composed of a network. Such electrical devices, especially storage structures for electricity, can be used as short-time or reverse power sources of current for, for example, radio electrical devices, personal computers, video and other devices. The present invention also relates to a method for manufacturing an electrode having a solid carbon skeleton network having a large number of pores and a capacitor electrode material. One of the main directions in the development of high efficiency capacitors with dual electrical layers is to create new electrode carbon materials with a combination of properties such as optimal pore size, mechanical strength and high chemical purity. Known in the art is a capacitor having a double electrical layer that includes a bi-polarized electrode separated by a separator and placed in an airtight frame (eg, Japanese Patent Application No. 3-62296). The electrodes are made of activated carbon and a binder (comprising carbon black and ceramic powder). The electrode material has a porous structure and produces a specific electrical capacitance of 25 F / cm ³ or less. The disadvantages of such capacitors are:-a considerable leakage current due to a large amount (3-8%) of ash in the electrical material;-changes in the microporous properties of the electrode material in the process of manufacturing the electrode and capacitor assembly. The mechanical properties of the electrode material are low (this limits the use of these capacitors in structures operating under conditions of high mechanical stress, for example vibration). Additionally, what is known in the art is a capacitor that includes a stainless steel frame, the frame having a dual electrical layer including a bottom and a lid joined by a washer, which creates an airtight container. The frame is provided with dipolar electrodes that are saturated with electrolyte and separated by a porous separator. The electrodes are made of activated carbon (80% by weight) and a binder (composed of ash (10% by weight) and polytetrafluoroethylene (10% by weight)). The material in the form of a paste is applied to the electrically conductive underlayer, then rolled and dried. An electrode of a specified size is cut from the generated sheet product. Such capacitors can operate over a wide temperature range. Electrode material gives a specific electric capacitance within the limits of 20-25F / cm ^3. However, these capacitors have all of the aforementioned disadvantages. Electrodes for a double-layer capacitor consisting of an interconnected solid network are known from EP-A1-066,345. SUMMARY OF THE INVENTION It is an object of the present invention to simultaneously increase the capacitor specific electrical capacitance, reduce the variation of the practical capacitance value and reduce the leakage current. It is a further object of the present invention to obtain an increase in electrode strength and mechanical stability. This would extend the area of use of the capacitor, for example, in structures that operate under mechanical shock or vibration conditions. In order to achieve this technical result, capacitors of the type mentioned at the beginning of the description have a structure in which the electrode has a pore volume of more than 55% of the electrode material volume, and the part of the pores having a size smaller than 10 nm is the electrode material. It is characterized by being 35-50% of the volume. The carbon content of the electrode is at least 95% by mass, preferably at least 99% by mass. The material preferably has a total pore volume in the range of 55-80% of the electrode volume, which makes it possible to obtain a high electrical capacitance. The present invention also relates to a method for producing an electrode having a solid carbon skeleton network having a large number of pores, comprising the steps of:-a metal carbide powder and an organic binder and carbon black as a binder. Forming an electrode blank of carbon in the form of or as a pyrolysis product (the amount of binder is 5-50 g per 100 g of metal carbide powder);-in a vacuum furnace above the melting temperature but above this temperature Saturating the blank formed by the liquid metal at a temperature not exceeding 300 ° C .; such as fluorine or chlorine at a temperature of 800-1200 ° C. for the formation of transport channels / pores and nanoporous (<10 nm) carbon structures. The blank saturated with the halogen gas is heat-treated. After such manufacture, the electrode contains substantially pure carbon with a transport channel / pore branching system and small amounts of impurities (less than 5% by weight, preferably less than 1% by weight). These electrodes have a carbon structure that provides high electrode mechanical strength (compression strength of 90 kg / cm ² or more). The material gives rise to mechanical stiffness and strength, a solid network of connected carbon throughout the structure, and a combination of coarse-sized transport channels / pores and nano-sized pores of the electrolyte that together make up the overall pore volume. Consists of Also important is the stability of the electrode dimensions and its pores, and consequently the stability of the electrode electrical properties. Thus, the reduction in height and diameter values from the intermediate product to the finished electrode is less than 0.05%, which allows for a very limited variation in electrode specific electrical capacitance resulting in a practical capacitor capacitance in the range of ± 15%. . On the other hand, conventional capacitors have an electrical capacitance tolerance of +80 to -20%. The new electrode provides a specific electrical capacitance of almost 30% and an increase in practical capacitor capacitance and a reduction of the leakage current by a factor of 5 to 10 compared to the prior art solution with only a low impurity content of the electrode material. . In addition, the high electrode strength allows it to be used for capacitors in devices that operate under vibration, shock and other mechanical stresses. The present invention will be described in more detail with reference to the illustrated embodiments and the accompanying drawings. FIG. 1 provides a depiction (side view) of the overall capacitor, and FIG. 2 provides a plot of load voltage versus discharge time. Claims 1. Includes at least two electrodes (4, 5) consisting essentially of porous carbon, said electrodes being substantially saturated with electrolyte and separated by a porous separator (6) having ion conductivity. In a double electric layer capacitor comprising a solid carbon network to which the electrodes (4, 5) are connected, the electrodes (4, 5) have a pore volume exceeding 55% of the electrode material volume and a size smaller than 10 nm. Characterized in that the portion of the pores having the following is 35-50% of the volume of the electrode material. 2. The capacitor according to claim 1, wherein the carbon content in the porous electrode is more than 95% by mass, preferably more than 99% by mass. 3. Capacitor according to claim 1 or 2, characterized in that the volume of the pores is in the range 55-80%, preferably 60-80%. 4. The capacitor according to claim 1, wherein the compressive strength of the electrode material exceeds 90 kg / cm ² . 5. A capacitor according to claim 1, wherein the electrodes are arranged in an airtight frame including a bottom (1) and a lid (2) joined by a dielectric washer (3). 6. The capacitor according to any one of claims 1 to 5, wherein the elastic washer (7) is provided so as to surround the periphery of the electrode. 7. Process for producing an electrode with a solid carbon skeleton network having a large number of pores, characterized by comprising the following steps:-metal carbide powder and organic binder as binder and carbon black or in the form of pyrolysis products Forming an electrode blank of carbon as (the amount of binder is 5-50 g per 100 g of metal carbide powder);-liquid at a temperature above the melting temperature in a vacuum furnace but not more than 300 ° C above this temperature Saturating blanks molded by metal; blanks saturated with halogen gases such as fluorine or chlorine at temperatures of 800-1200 ° C. for the formation of transport channels / pores and nanoporous (<10 nm) carbon structures. Is heat-treated. 8. The method according to claim 7, wherein a metal is selected from the group IV, V or VI of the periodic system or from aluminum or silicon. 9. The method of claim 8, wherein an electrode blank of silicon carbide powder and a binder is formed. Ten. Electrodes from either silicon carbide powder and a mixture consisting essentially of 30-50% by weight carbon black as binder, 5-10% by weight phenol formaldehyde resin and 40-60% by weight ethylated alcohol, or pyrocarbon 10. The method of claim 9, wherein the blank is formed and the amount of binder is 5-50 g per 100 g of silicon carbide powder. 11． 11. A method according to claim 9 or 10, characterized in that it comprises the following steps:-saturating the electrode blank with liquid silicon at a temperature of 1450-1700C in a vacuum furnace;-transport channels / pores and nanoporous ( <10 nm) Heat the saturated blank with chlorine at a temperature of 900-1100 ° C. to form a carbon structure. 12． In a capacitor electrode material consisting essentially of porous carbon comprising a connected solid carbon network, a portion of pores having a pore volume exceeding 55% of the electrode material volume and having a size smaller than 10 nm is a volume of the electrode material volume. 35-50% of the total weight of the capacitor electrode material. 13. 13. The capacitor electrode material according to claim 12, wherein the carbon content is more than 95% by mass, preferably more than 99% by mass.

────────────────────────────────────────────────── ─── Continuation of front page    (81) Designated countries EP (AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, M C, NL, PT, SE), OA (BF, BJ, CF, CG , CI, CM, GA, GN, ML, MR, NE, SN, TD, TG), AP (KE, LS, MW, SD, SZ, U G), UA (AZ, BY, KG, KZ, RU, TJ, TM ), AL, AM, AT, AU, AZ, BB, BG, BR , BY, CA, CH, CN, CZ, DE, DK, EE, ES, FI, GB, GE, HU, IS, JP, KE, K G, KP, KR, KZ, LK, LR, LS, LT, LU , LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, S I, SK, TJ, TM, TR, TT, UA, UG, US , UZ, VN (72) Inventor Goldef, Sergey Constantino             Vitch             Russian Federation, 193076 St. Petersburg             Rug, Lyavacki Prospect 19,             House 1, APM27 (72) Inventors Tsukov, Sergei Germanovich             Russian Federation, 193030 St. Petersburg             Lug, Tielnisowski Square             8, APTM 41 (72) The inventor Zelenov, Boris Alexandrovi             Switch             Russian Federation, 198288 St. Petersburg             Lug, Dimitrov Street 31/1,             APM 322 (72) Inventors Kraftik, Alexander Effi             Movic             Russian Federation, 198097 St. Petersburg             Lug, Statik Prospect 11,             APM 48 (72) Kuznetsov, Victor Peterovich             H             Russian Federation, 194356 St. Petersburg             Lug, Jesenin Street 26, House               1, APTM 419 (72) Inventors Kukskina, Julia Alexandrov             Na             Russian Federation, 196160 St. Petersburg             Lug, Borisie Oktinsky Pro             Spect 14, APM 143 (72) Inventors Mazaeva, Tatyana Vasilevna             Russian Federation, 195208 St. Petersburg             Lug, Cosidzin Prospect 30, C             Us 2, APTM 135 (72) Inventor Pankina, Olga Cergyvna             Russian Federation, 194037 St. Petersburg             Lug, Engels Prospect 128,             APM 317 (72) Inventor Sokolov, Vassilii Vasilevic             Russian Federation, 198096 St. Petersburg             Lug, Tielneuj Kazacestovo             Street 8, APM 25

Claims (1)

Claims 1. A dual electric device comprising at least two electrodes substantially consisting of porous carbon, said electrodes being substantially saturated with an electrolyte and separated by a porous separator having ionic conductivity. In the multilayer capacitor, the electrodes (4,5) in the form of a porous structure are made of a material having a carbon content of more than 95% by mass and a pore volume of more than 55% of the electrode material volume, wherein a certain part of the pores is formed. A double electric layer capacitor having a size smaller than 10 nm. 2. The capacitor according to claim 1, wherein the carbon content exceeds 99% by mass. 3. Capacitor according to claim 1 or 2, characterized in that the volume of the pores is in the range 55-80%, preferably 60-80%. 4. The capacitor according to claim 1, wherein the volume of the pores having a size smaller than 10 nm is 35 to 50% of the volume of the electrode material. 5. The capacitor according to claim 1, wherein the compressive strength of the electrode material exceeds 90 kg / cm ² . 6. The electrode is made of metal carbide powder and an organic binder as binder and carbon, for example in the form of carbon black or as a pyrolysis product, the amount of binder preferably being 5 to 50 g per 100 g of metal carbide powder The capacitor according to any one of claims 1 to 5, wherein the electrode blank is formed from a metal carbide powder and a binder. 7. The capacitor of claim 6, wherein said electrode is made from a blank by a chemical heat treatment comprising the steps of:-at a temperature above the melting temperature in a vacuum furnace but not above 300 ° C. Saturation with liquid metal; heat treatment in a halogen gas such as fluorine or chlorine at a temperature of 800-1200 ° C. for the formation of transport channels / pores and nanoporous (<10 nm) carbon structures. 8. A capacitor according to claim 6 or 7, wherein the metal is selected from the group IV, V or VI of the periodic system or from aluminum or silicon. 9. A capacitor according to claim 1, wherein each electrode is made from a blank substantially containing silicon carbide and a binder by chemical heat treatment. Ten. Either a mixture of pyrocarbon or pyrocarbon in which the electrode consists essentially of silicon carbide powder and 30-50% by weight carbon black, 5-10% by weight phenol formaldehyde resin and 40-60% by weight ethylated alcohol as binder. 10. A capacitor according to claim 9, wherein the amount of binder is preferably 5-50 g per 100 g of silicon carbide powder and the electrode blank is formed from silicon carbide powder and binder. 11． 11. Capacitor according to claim 9 or 10, characterized in that the electrode is made from a blank by a chemical heat treatment comprising the following steps:-saturation with liquid silicon at a temperature of 1450-1700C in a vacuum furnace; Heat treatment with chlorine at a temperature of 900-1100 ° C. to form pores and nanoporous (<10 nm) carbon structures. 12． 12. The capacitor according to claim 1, wherein the electrodes are arranged in an airtight frame including a bottom (1) and a lid (2) joined by a dielectric washer (3). 13. The capacitor according to any one of claims 1 to 12, wherein the elastic washer (7) is provided so as to surround the periphery of the electrode. 14. Capacitor electrode material characterized by connecting a solid carbon network comprising a combination of transport channels / pores and nanoporosity (<10 nm). 15． 15. Material according to claim 14, characterized in that the carbon content is greater than 95% by mass, preferably greater than 99% by mass. 16． 16. A porous carbon as a capacitor according to any one of claims 1 to 15, wherein an electrode structure network of solid carbon is produced by making an electrode from a blank substantially containing metal carbide powder and a binder by chemical heat treatment. The method of manufacturing the material.