Use of zeolite-templated carbon (ZTCS) as an electrode for supercapacitors

Abstract

ZTC is used as an active material for electrodes in supercapacitors. ZTC is produced from a CaX or NaX template. Carbon deposition is performed using acetylene, ethanol, or propylene. The ZTC-zeolite composition is graphitized, cooled, and acid washed to remove the zeolite template. ZTC produced from this method is characterized by a high surface area and is operable for use as an active material in supercapacitors. The supercapacitor can also include an H2SO4 electrolyte.

Description

[Technical Field]

[0001] The present disclosure relates to the use of zeolite-templated carbon (ZTC). Specifically, disclosed herein are supercapacitor electrodes formed from ZTC and methods used to form ZTC. [Background technology]

[0002] A supercapacitor is an electrochemical capacitor that stores electrical energy. Compared to conventional batteries or conventional capacitors, supercapacitors have lighter weight, faster discharge, faster charge, longer charge cycle life, and superior temperature performance. The performance of a supercapacitor is related to several factors, including the electrolyte selection and electrode material composition. Because capacitance is proportional to the surface area of ​​the electrode, electrochemically inert materials with large specific surface areas are utilized. Conventional electrode materials include activated carbon, metal oxides, or graphite.

[0003] Conventional electrode materials lack uniform pores and channels or have "dead pores" that prevent ion exchange. Furthermore, conventional materials are difficult to manufacture consistently in large batches and can have inconsistent manufacturing results. Therefore, there is a need for high-capacity, high-surface-area materials for use as supercapacitor electrodes. Summary of the Invention

[0004] Disclosed herein is a method for producing zeolite-templated carbon (ZTC) for use as an active material in a supercapacitor electrode. The method includes providing CaX zeolite at a selected size and depositing carbon on the CaX zeolite using an organic precursor in a plug flow reactor to produce a ZTC-zeolite composition. The carbon deposition is carried out at an elevated temperature. The method also includes cooling the ZTC-zeolite composition; heating the ZTC-zeolite composition by introducing an inert gas stream for a predetermined time, where the ZTC is heated to a graphitization temperature of 820 to 1180 K to produce a graphitized ZTC-zeolite composition; cooling the graphitized ZTC-zeolite composition; and washing the graphitized ZTC-zeolite composition with an acid to produce a prepared ZTC. The prepared ZTC can be used as an active material in a supercapacitor electrode and has a selected surface area. In some embodiments, the inert gas stream is a helium stream containing helium. In some embodiments, the inert gas stream is a nitrogen stream that comprises nitrogen. The inert gas stream is heated.

[0005] In some embodiments, the organic precursor is selected from the group consisting of propylene, ethanol, acetylene, and combinations thereof. In other embodiments, the organic precursor comprises propylene. In some embodiments, the acid is selected from the group consisting of HCl, HF, and combinations thereof. The method also includes drying the prepared ZTC. In some embodiments, the prepared ZTC defines micropores of 1.5-2 nm and mesopores of 2-5 nm. The temperature is in the range of 800K to 1080K.

[0006] Further disclosed herein is a supercapacitor including an electrode, the electrode including an active material and a metal component. The active material includes zeolite-templated carbon (ZTC) produced by the methods claimed herein. The supercapacitor also includes an electrolyte including H2SO4 and a membrane separator.

[0007] In some embodiments, the supercapacitor retains up to 75% of its capacitance at a high current density of 15 A / g. In some embodiments, the ZTC is 2500m 2 / g~3000m 2 / g. In some embodiments, the ZTC is in the range of 1.0 cm 3 In some embodiments, the supercapacitor has a capacitance in the range of 100 to 250 F / g.

[0008] Further disclosed herein is a method for producing zeolite-templated carbon (ZTC) for use as an active material in an electrode of a supercapacitor. The method includes the steps of providing NaX zeolite, and adsorbing the NaX zeolite and CA +2 The method includes initiating ion exchange with ions to produce large crystalline calcium (LCaX) zeolite, and using acetylene to deposit carbon on the LCaX zeolite in a plug flow reactor to produce a ZTC-zeolite composition. The carbon deposition is performed at an elevated temperature. The method also includes cooling the ZTC-zeolite composition; heating the ZTC-zeolite composition by introducing an inert gas flow for a predetermined time, wherein the ZTC is heated to a graphitization temperature in the range of 820 K to 1180 K to produce a graphitized ZTC-zeolite composition; cooling the graphitized ZTC-zeolite composition; and washing the graphitized ZTC-zeolite composition with an acid to produce a prepared ZTC. The prepared ZTC can be used as an active material in an electrode of a supercapacitor and has a selected surface area. In some embodiments, the inert gas flow is a helium flow. The inert gas flow is heated.

[0009] In some embodiments, the elevated temperature is in the range of 820 K to 873 K. In some embodiments, the method also includes depositing a second carbon layer on the graphitized ZTC-zeolite composition using acetylene. The second carbon layer is deposited at an elevated temperature. In some embodiments, the elevated temperature is in the range of 800 K to 873 K. In some embodiments, the acid is selected from the group consisting of HCl, HF, and combinations thereof. [Brief explanation of the drawings]

[0010] These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following description, claims, and accompanying drawings, in which it should be noted, however, that the drawings illustrate only some embodiments of the invention and therefore should not be considered as limiting the scope of the invention, as other equally effective embodiments may be recognized.

[0011] [Figure 1] FIG. 1 is a simplified diagram of a supercapacitor.

[0012] [Figure 2] 1 is a graph of NH3 temperature programmed desorption profiles of CaX and commercial NaX, according to one embodiment.

[0013] [Figure 3] 1 is a graph of X-ray diffraction pattern results for selected ZTC, according to one embodiment.

[0014] [Figure 4] 1 is a graph of N2 adsorption and desorption isotherms for selected ZTCs, according to one embodiment.

[0015] [Figure 5] 1 is a graph of pore size distribution of selected ZTCs, according to one embodiment.

[0016] [Figure 6] 1 is a graph of N2 adsorption / desorption isotherms for a ZTC-zeolite composition of LCaX-produced ZTC, according to one embodiment.

[0017] [Figure 7A] 1 is a graph of N2 adsorption / desorption isotherms for LCaX-produced ZTC, according to one embodiment.

[0018] [Figure 7B]1 is a graph of pore size distribution of LCaX-produced ZTC, according to one embodiment.

[0019] [Figure 7C] 1 is a graph of an X-ray diffraction pattern of LCaX-produced ZTC, according to one embodiment.

[0020] [Figure 8A] 1 is a graph of X-ray diffraction patterns comparing propylene-based ZTC with commercially available activated carbon, according to one embodiment.

[0021] [Figure 8B] 1 is a graph of N2 adsorption / desorption isotherms comparing propylene-based ZTC with commercially available activated carbon, according to one embodiment.

[0022] [Figure 9A] 1 is a graph of the cyclic voltammetry response of an electrode including propylene-based ZTC and a commercially available activated carbon, according to one embodiment.

[0023] [Figure 9B] 1 is a graph of specific discharge capacity as a function of current density comparing propylene-based ZTC with a commercially available activated carbon, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] While the present disclosure is described using several embodiments, it should be understood that those skilled in the art will appreciate that many variations, modifications, and variations of the systems and methods described are within the scope and spirit of the present disclosure. Accordingly, the described embodiments of the invention are set forth without loss of generality and without limiting the scope of the claims.

[0025] Terms such as "consisting of," "including," and "having," when used in reference to embodiments of the present invention, are synonymous and are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps. "Optional" or "optionally" means that an element may be used in some embodiments but may be omitted in other embodiments. The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0026] A method for producing ZTC and a supercapacitor using ZTC as the active material of the electrode are disclosed. ZTC is produced using CaX zeolite as a template, carbon deposition, and various organic precursors. Supercapacitors using ZTC as an electrode have a specific capacitance that is twice that of conventional electrodes in supercapacitors. The supercapacitors disclosed herein can retain 75% of their capacitance even at a high current density of 15 A / g, which is superior to conventional activated carbon electrodes. The resulting ZTC can, in some embodiments, be used for electrochemical reactions up to 3000 m 2 ZTC is also characterized by a high surface area of ​​over 1 cm 3 / g。 ZTC can have a large micropore volume of more than 10 ...

[0027] A supercapacitor functions as an electric double layer capacitor and is characterized by electrodes, an electrolyte, and a separator. Referring to FIG. 1, a simplified supercapacitor 100 is shown. The current collector 102 collects ions of the appropriate charge (positive on the positive side and negative on the negative side). The current collector 102 is made of a material that is highly conductive, has low contact resistance with the electrode, and forms a strong and stable bond with the electrode. The current collector 102 is also compatible with the electrolyte and will not corrode or react with the current collector 102 while the system is operating. The current collector 102 can be made of aluminum foil, which conducts current from the electrode. The aluminum foil also supports the electrode. The electrolyte 104 allows for the transfer of charge. In some embodiments, the electrolyte 104 is H2SO4. In some embodiments, hydroquinone is added to the electrolyte. The electrode 106 accumulates charged particles on its surface. In the embodiments disclosed herein, the electrode 106 is ZTC produced using the methods disclosed herein. The separator 108 physically separates the electrodes to prevent short circuits, but allows the mobility of charged ions while preventing electronic conductance. The separator 108 is a thin material, which can be a few hundredths of a millimeter, and is porous to conductive ions. The separator 108 is chemically inert to protect and preserve the stability and conductivity of the electrolyte. The separator 108 can be a membrane separator. Other suitable materials for the separator 108 include open capacitor paper and porous polymer membrane nonwovens, including materials such as polyacrylonitrile, woven glass fibers, porous woven ceramic fibers, or combinations thereof.

[0028] The electrode includes an active material characterized by a high surface area and a metal current collector characterized by high electrical conductivity. The metal current collector can include materials similar to those of the current collector 102. Energy storage in a supercapacitor relies on the physical adsorption of electrolyte ions on the surface of the carbon electrode, with the stored energy being proportional to the number of ions absorbed on the electrode surface. Therefore, electrodes with carbon materials characterized by a high surface area provide a high specific / volume energy density. Uniform porosity with a three-dimensionally connected micropore structure provides a significantly high power density for the supercapacitor due to the high rate of ion transport within the micropore structure.

[0029] In embodiments disclosed herein, the electrode comprises ZTC as an active material. ZTC that can be used as a superconductor in the embodiments described herein includes ZTC characterized by both micropores and mesopores. In preferred embodiments disclosed herein, the ZTC is characterized substantially only by micropores, such that the ZTC pores are primarily contained and concentrated in the micropore region. Micropores have diameters of about 2 nanometers or less. Mesopores have diameters of about 2 nanometers to about 5 nanometers. Macropores have diameters greater than about 5 nanometers. In embodiments disclosed herein, ZTC utilized as an active material in a supercapacitor is characterized by enhanced microporosity and consistent interconnected micropores, resulting in improved supercapacitor performance.

[0030] The ZTC disclosed herein is produced in a process using a zeolite as a template. A zeolite of a selected size is used as the template. The selected size can be small or large crystal morphology. The small crystal morphology can be in the 1-2 μm range, and the large crystal morphology can be in the 10-20 μm range. In some embodiments, NaX is the zeolite used in producing ZTC. In some embodiments, 1 g of zeolite is added to a plug flow reactor. A heated inert gas stream is introduced into the zeolite to elevate its temperature. The heated inert gas stream can be a helium stream containing substantially helium, and the helium stream can contain impurities that do not substantially affect the process. The heated inert gas stream can be a nitrogen stream containing substantially nitrogen, and the nitrogen stream can contain impurities that do not substantially affect the process. The heated inert gas stream heats the zeolite. Advantageously, helium or nitrogen can be used throughout the process to provide an inert environment and provide other benefits, such as further dehydrogenation of the composition for graphitization. The temperature increase can range from 800K to 1080K, alternatively 820K to 1180K, alternatively 823K to 873K, alternatively 823K to 973K, alternatively 823K to 1073K, alternatively 870K to 1023K, alternatively 873K to 973K, alternatively 873K to 1023K. In some embodiments, the temperature increase ranges from 970K to 1000K. In some embodiments, the temperature increase is 823K, alternatively 873K, alternatively 973K, alternatively 1023K, or alternatively 1073K.

[0031] After the zeolite is heated and held for a period of time, in some embodiments 30 minutes, a stream containing one or more organic precursors is introduced into the ZTC. The organic precursors can be heated. As they pass through the bed, the organic precursor temperature reaches the same temperature as the zeolite. In some embodiments, the organic precursors include propylene, ethanol, acetylene, or a combination thereof. In some embodiments, the organic precursor is acetylene. In a preferred embodiment, the organic precursor is propylene. Carbon is deposited into the template by carbon deposition in a plug flow reactor. The organic precursors form a three-dimensional negative of the zeolite template woven between the channels of the zeolite, producing the ZTC-zeolite composition. After a period of time, the flow of organic precursors is stopped, and the temperature of the zeolite template is reduced to room temperature using a helium flow. In some embodiments, the carbon deposition time is 2-9 hours, alternatively 4-9 hours, or alternatively 4-5 hours. In some embodiments, the carbon deposition time is 2 hours, alternatively 4 hours, alternatively 5 hours, alternatively 6 hours, or alternatively 9 hours.

[0032] In some embodiments, the ZTC-zeolite composition is further heated to graphitize the ZTC. This heating can be accomplished with a heated second inert gas stream, such as a heated helium stream or a heated nitrogen stream. The heated helium or nitrogen stream can also further dehydrogenate the ZTC-zeolite composition for graphitization. The temperature for graphitization can range from 820 K to 1180 K, or alternatively, from 1100 K to 1180 K. In some embodiments, the temperature for graphitization is 1123 K. In some embodiments, the temperature for graphitization is 1173 K. In some embodiments, the graphitization time is 4 hours. In some embodiments, the graphitization time is 2 to 9 hours. The ZTC-zeolite composition is then cooled and acid washed. The zeolite is dissolved by the acid to leave behind the ZTC. The ZTC-zeolite composition is acid washed with HCl, HF, or a combination thereof for 1 hour to remove the zeolite and produce ZTC. In some embodiments, the acid wash is performed twice. After the acid wash, the ZTC is rinsed with water and dried. In some embodiments, drying is performed at 373K.

[0033] In a preferred embodiment, CaX is utilized as the zeolite for the production of ZTC for use in supercapacitor electrodes. CaX is produced by ion exchange on commercial-grade NaX zeolite. In some embodiments, a 10 ml sample of NaX is added to 200 mL of 0.32 M Ca(NO3)2 solution and stirred for 4 hours. Commercial-grade NaX zeolite is readily available and is not characterized by large or extra-large crystal morphology. In some embodiments, the produced CaX has small crystals in the 1-2 μm range.

[0034] Advantageously, CA +2The use of CaX produced by exchange can create acidic sites in the zeolite, which catalyze carbon deposition within the zeolite micropores, allowing for selective carbon deposition within the micropores. The creation of acidic sites beneficially increases the thermal stability of the zeolite template during the carbon deposition process, resulting in more consistent ZTC production and higher quality ZTC.

[0035] Referring to Figure 2, the NH3 temperature programmed desorption profiles of CaX and commercial NaX are shown. CaX exhibits two desorption peaks at 473 K and 653 K. These two desorption peaks indicate the presence of two different types of acid sites. NaX does not exhibit a desorption profile and therefore does not exhibit acid sites.

[0036] Additionally, as shown in Table 1 below, the acid sites create thermal stability in the template during carbon deposition.

[0037] [Table 1]

[0038] In Table 1, A z is the equivalent fraction of exchanged cations in the zeolite, and T init is the temperature in K at which structural degradation is first observed from the X-ray diffraction pattern, and T 0.5 is the temperature in K at which the structure is decomposed by 50%. Advantageously, the increased stability of CaX at temperatures such as 973 K allows for the utilization of CaX zeolites in higher temperature carbon deposition processes.

[0039] In some embodiments, CaX can be prepared according to the methods described herein and utilized as a zeolite in the production of numerous ZTCs. Propylene and ethanol can be utilized as organic precursors. In some embodiments, the organic precursor stream is 2% by volume propylene in an inert gas stream saturated with ethanol using a 6 kPa bubbler. In some embodiments, the organic precursor stream is 2% by volume acetylene in an inert gas stream. In other embodiments, a pure propylene stream or an ethanol stream is utilized as the organic precursor. In some embodiments, the organic precursor can be either propylene or ethanol and can have a concentration of 3-5% by volume in the inert gas stream. In some embodiments, the organic precursor stream is 2% by volume propylene in a helium stream saturated with ethanol using a 6 kPa bubbler. In some embodiments, the organic precursor stream is 2% by volume acetylene in a helium stream. In other embodiments, a pure propylene or ethanol stream is utilized as the organic precursor. In some embodiments, the organic precursor can be either propylene or ethanol and can have a concentration of 3-5% by volume in a helium stream. In some embodiments, the organic precursor stream is 10% by volume propylene in a N stream. The flow rate of the organic precursor is 200 mL / min-g. (zeolite) It could be.

[0040] The organic precursor is utilized for carbon deposition at a specific temperature for a specific time, which may vary. In some preferred embodiments, the specific temperature is in the range of 823K to 1073K, alternatively in the range of 823K to 873K, or alternatively in the range of 1023K to 1073K. The specific temperature may be 800K to 1080K, alternatively in the range of 820K to 1180K, alternatively in the range of 823K to 873K, alternatively in the range of 823K to 973K, alternatively in the range of 823K to 1073K, alternatively in the range of 870K to 1023K, alternatively in the range of 873K to 973K, or alternatively in the range of 873K to 1023K. In some embodiments, the specific temperature may be in the range of 970K to 1000K. In some embodiments, the specific temperature is 823K, alternatively in the range of 873K, alternatively in the range of 973K, alternatively in the range of 1023K, or alternatively in the range of 1073K. In some embodiments, the carbon deposition time ranges from 2 to 9 hours, alternatively from 4 to 9 hours, alternatively from 4 to 5 hours. In some embodiments, the carbon deposition time is 2 hours, alternatively from 4 hours, alternatively from 5 hours, alternatively from 6 hours, or alternatively from 9 hours. The ZTC-zeolite composition can be rinsed twice for 1 hour at room temperature with an aqueous solution of HCl, HF, and 3.4 wt% HCl and 3.3 wt% HF. The material is filtered, washed, and dried at a drying temperature. In some embodiments, the drying temperature is 373 K. Embodiments of ZTC produced using the methods disclosed herein are listed in Table 2 below.

[0041] [Table 2]

[0042] Referring to Figure 3, the X-ray diffraction patterns for selected ZTCs in Table 2 show a broad peak at 2θ = 5-6°, indicating the presence of structural order in the micropore array. CaX-973P5 exhibits the highest resolved peak, indicating the most faithful replication of the CaX template.

[0043] Referring to Figure 4, N adsorption and desorption isotherms for selected ZTCs in Table 2 are shown. Referring to Figure 5, pore size distributions for selected ZTCs in Table 2 are shown. Figures 4 and 5 show that ZTCs exhibit dual porosity, with both micropores in the 1.5-2 nm diameter range and mesopores in the 2-5 nm diameter range. The distributions were calculated using a nonlocal density functional theory algorithm. The Brunauer-Emmett-Teller (BET) surface areas and pore volumes (micropores, mesopores, and total) for selected ZTCs are shown in Table 3 below.

[0044] [Table 3]

[0045] In Table 3, V is calculated using the DR formula. micro (cm 3 / g) is calculated. As shown in Table 3 and Figures 4 and 5, 3 The presence of mesopores larger than 1000 / g indicated that the micropore structure of CaX was not faithfully replicated in some areas, since CaX is characterized only by micropores. This is likely due to the incomplete filling of the micropores in the zeolite structure with carbon. CaX-1023A2 in Table 3 features a larger surface area and the highest micropore volume compared to other ZTCs produced using acetylene carbon precursors. Without being bound by theory, it is believed that the small kinetic diameter of acetylene results in the most faithful replication of the zeolite of the three organic precursors disclosed herein.

[0046] In some embodiments, ZTC is produced using acetylene as a carbon precursor for carbon deposition utilizing large crystallite CaX (LCaX). LCaX can have large crystallite sizes in the 10-20 μm range. Advantageously, the use of LCaX provides improved reproducibility, the ability to scale up production when more than 1 g of zeolite is utilized, the ability to have more practical and consistent properties, and better commercial applications.

[0047] During carbon deposition of LCaX, the temperature may range from 800K to 1080K, alternatively from 820K to 1180K, alternatively from 823K to 873K, alternatively from 823K to 973K, alternatively from 823K to 1073K, alternatively from 870K to 1023K, alternatively from 873K to 973K, alternatively from 873K to 1023K. In some embodiments, the temperature may range from 970K to 1000K. In some embodiments, the temperature may be 823K, alternatively from 873K, alternatively from 973K, alternatively from 1023K. In some embodiments, the zeolite-ZTC composition is heat treated after carbon deposition for the purpose of graphitization. Graphitization may be performed using a noble gas. Graphitization may be performed using an inert gas. The noble gas may include helium. The inert gas may include nitrogen. The graphitization temperature may be 1123K or lower. In some embodiments, the graphitization temperature ranges from 1100 K to 1180 K. In some embodiments, the graphitization temperature ranges from 820 K to 1180 K. In some embodiments, the graphitization temperature ranges from 1123 K to 1173 K. In some embodiments, the graphitization temperature is 1123 K. In some embodiments, the graphitization temperature is 1173 K. In further embodiments, a second carbon deposition is performed, optionally followed by a second graphitization. The temperatures of the second carbon deposition and graphitization may be different or the same as the temperatures of the first carbon deposition and graphitization.

[0048] In some embodiments, more than one carbon deposition is performed. In these embodiments, the ZTC-zeolite composition is cooled after the first carbon deposition. The ZTC-zeolite composition is reheated and a second carbon deposition is performed. Additional cycles can be performed. After the carbon deposition cycle is complete, the ZTC-zeolite composition is cooled and acid washed to produce ZTC.

[0049] Embodiments of LCaX-produced ZTC are disclosed below in Table 4. These embodiments utilized acetylene as the organic precursor.

[0050] [Table 4]

[0051] The Brunauer-Emmett-Teller (BET) surface areas and pore volumes (micropore, mesopore, and total) for selected LCaX-produced ZTCs are shown in Table 5 below.

[0052] [Table 5]

[0053] In Table 5, V is calculated using the DR formula. micro (cm 3 The calculated surface area (µm / g) is used. Table 5 shows that higher carbon deposition temperatures result in higher surface areas and larger micropore volumes. Lower temperatures, such as the 873 K temperature used in LCaX-873-4, result in lower surface areas. However, heat treatment results in higher surface areas and larger micropore volumes. Without being bound by theory, it is believed that graphitizing the sample by heat treatment results in maintaining a highly micropore structure so that the structure does not collapse after the zeolite is removed. The data in Table 5 also show that carbon deposition using acetylene is sensitive to increasing the starting amount of zeolite template due to increased bed thickness. Thus, LCaX-1023-2b exhibits reduced surface area and micropore volume compared to LCaX-1023-2a, even though only the starting amount of zeolite template utilized differs.

[0054] In some embodiments, continuous carbon synthesis is utilized to produce ZTC. Advantageously, continuous carbon synthesis overcomes some of the scalability barriers of acetylene-based carbon deposition disclosed above. In some embodiments, a first acetylene-based carbon deposition is performed at a first temperature, followed by graphitization at a graphitization temperature. The first temperature can be 873 K or less. In some embodiments, the first temperature is in the range of 800 K to 873 K. In preferred embodiments, the first temperature is in the range of 823 K to 873 K. The 823 K to 873 K range is considered the optimal temperature for the initial acetylene-based carbon deposition due to the synthesis of increased surface area and larger micropore volume. In other embodiments, the temperature may range from 800K to 1080K, alternatively from 820K to 1180K, alternatively from 823K to 873K, alternatively from 823K to 973K, alternatively from 823K to 1073K, alternatively from 870K to 1023K, alternatively from 873K to 973K, alternatively from 873K to 1023K.

[0055] Graphitization can be performed using a noble gas. Graphitization can be performed using an inert gas. The noble gas can include helium. The inert gas can include nitrogen. The graphitization temperature can be 1123 K or lower. In some embodiments, the graphitization temperature ranges from 1100 K to 1180 K. In some embodiments, the graphitization temperature ranges from 820 K to 1180 K. In some embodiments, the graphitization temperature ranges from 1123 K to 1173 K. In some embodiments, the graphitization temperature is 1123 K. In some embodiments, the graphitization temperature is 1173 K. In further embodiments, a second carbon deposition can be performed, optionally followed by a second graphitization. The temperatures of the second carbon deposition and graphitization can be different or the same as the temperatures of the first carbon deposition and graphitization.

[0056] Without being bound by theory, it is believed that acetylene deposition at lower temperatures, such as 873 K, results in uniform carbon deposition throughout the zeolite bed, while heating the composition at 1123 K under an inert gas, such as helium, results in densification and graphitization of the carbon structure. This combination results in uniform and selective desorption of highly graphitized carbon within the zeolite micropores, resulting in high surface area and high micropore volume. Without being bound by theory, it is believed that incomplete filling of the zeolite template micropores results in the formation of mesopores in ZTC.

[0057] Referring to Figure 6, N adsorption / desorption isotherms of ZTC-zeolite compositions for LCaX-produced ZTC (before removal of the zeolite template by acid washing) are shown. The ZTC-zeolite composition LCaX-873-4 exhibits negligible microporosity remaining within the zeolite template, indicating that, theoretically, the zeolite micropores are completely filled with the ZTC carbon framework. The results for the ZTC-zeolite composition LCaX-873-4H show that after heat treatment at 1123 K for 4 hours to graphitize the carbon structure, approximately 25% of the zeolite micropore volume is regenerated, further indicating that the heat treatment results in densification and volumetric shrinkage of the ZTC carbon framework within the zeolite template micropores. Due to the regeneration of zeolite micropore volume, a second carbon deposition, optionally followed by a second graphitization, may be advantageous. Figure 6 shows that the micropores of the zeolite template in the LCaX-873-4H4H ZTC-zeolite composition are completely filled with the graphitized ZTC carbon framework. After acid washing, the LCaX-873-4H4H ZTC retains its surface area but exhibits a decrease in mesopore volume. As shown in Table 5 and Figure 6, a comparison of the properties of LCaX-873-4H4Ha and LCaX-873-4H4Hb demonstrated that continuous carbon synthesis allows for consistent reproduction of the carbon structure in ZTC, regardless of the amount of zeolite utilized or the bed thickness of the zeolite in the reactor.

[0058] Figures 7A, 7B, and 7C show the N adsorption isotherms and X-ray diffraction patterns of the LCaX-produced ZTC. LCaX-873-4H4H appears to be the most faithfully replicated carbon structure, exhibiting a type I isotherm with a small amount of N adsorption in the high-pressure region (P / P > 0.1). LCaX-873-4H exhibits a higher total pore volume than LCaX-873-4H4H due to the presence of secondary mesoporosity, as indicated by more pronounced adsorption at P / P > 0.1. LCaX-873-4H and LCaX-873-4H4H exhibit a narrower and more intense pore size distribution in the micropore region (2 nm). LCaX-873-4H4H exhibits a very sharp peak at 2θ = 6.3° in X-ray diffraction, indicating that the replicated carbon possesses a regular micropore structure similar to that of the zeolite template. Therefore, the presence of a sharp X-ray diffraction peak at 2θ = 6.3° can be used as an indicator to judge the faithful replication of the zeolite structure and the efficiency of carbon deposition. Finally, the isotherm and X-ray diffraction pattern results of LCaX-produced ZTC show that the pores are concentrated in the micropore region with a sharp peak at less than about 2 nanometers.

[0059] Supercapacitors featuring electrodes containing ZTC produced from the methods disclosed herein can exhibit substantial performance improvements over conventional supercapacitors that utilize activated carbon as the electrode active material. ZTC produced from carbon deposition of a propylene organic vapor precursor can be utilized as the electrode active material. In some embodiments, the propylene organic vapor precursor is 10% propylene in a N gas stream. In some embodiments, after carbon deposition, the ZTC-zeolite composition is graphitized by heat treatment as described herein.

[0060] The ZTC in the examples was synthesized from CaX using 10 vol% propylene in a N2 gas flow as the organic precursor and used as the electrode material. A bubbling fluidized-bed reactor was used to continuously stir the zeolite, enabling rapid heat transfer during the carbon deposition process. Bead-type NaX zeolite with a particle size distribution of 400-800 μm was obtained from Shanghai Jiuzhou Chemicals. For the examples, 250 g of NaX zeolite was placed in a quartz tube with an inner diameter of 70 mm and a tube height of 1 m. The temperature was raised to 973 K under a nitrogen flow of 3 L / min, then the nitrogen flow was changed to a flow of 2-30 L / min, and the temperature was maintained for 15 min. Propylene was co-injected with nitrogen at a ratio of 3.2 vol% propylene / N2. Some examples used 10 vol% propylene in a nitrogen flow. After carbon deposition using propylene, the ZTC-zeolite composition was graphitized by heat treatment at 1173 K. The reactor was heated with nitrogen at a rate of 2 L / min with a temperature increase of 2 K / min. The temperature was held for 3 hours to allow densification of the deposited carbon framework. After cooling to room temperature, the ZTC-zeolite composition was acid washed twice with a composition of 0.2 M HCl and 0.48 M HF and dried at 373 K overnight.

[0061] The ZTC characteristics produced and utilized in supercapacitor electrodes produced from the methods outlined above are approximately 3056 m 2 / g surface area, 1.12 cm 3 / g micropore volume, and 1.72 cm 3 / g total pore volume.

[0062] The propylene-based ZTC was compared with an activated carbon called YP-50F, available from Kuraray Chemical Co., Ltd. (see Figures 8A and 8B). X-ray diffraction and N adsorption / desorption isotherms for the propylene-based ZTC and YP-50F are shown. The propylene-based ZTC has a surface area of ​​1665 m. 2 / g and a micropore volume of 0.66 cm 3 / g, compared to YP-50F, which showed 2700m 2 / g and a very large surface area of ​​0.99 cm 3 / g micropore volume.

[0063] The capacitive performance of propylene-based ZTC was investigated against that of YP-50F in capacitor applications. ZTC was synthesized on a large scale using the procedure outlined above in a bubbling fluidized bed reactor with a 10% by volume propylene / nitrogen mixture. To further graphitize the deposited carbon skeleton, a heat treatment was carried out at 1173 K for 3 hours. The resulting ZTC was designated "ZTC-15Lmin" -1 The resulting ZTC was tested at -1173 K using the electrode. These results were compared with those of an electrode produced using a commercially available activated carbon, YP-50F (Kuraray Chemical Co., Ltd.), as a reference material. The propylene-based ZTC and YP-50F were tested using a 1 M H2SO4 electrolyte in a 2032-type two-electrode coin cell (provided by MTI) with a 20 mm diameter and 3.2 mm height. The working electrode was prepared by mixing ZTC or YP-50F with polyvinylidine fluoride (PVDF) binder and commercially available carbon black (Super P® from TIMCAL Graphite & Carbon) in N-methyl-2-pyrrolidone (NMP). The weight ratio of active material:PVDF:carbon black was 7:1:2. The slurry was applied to a stainless steel foil (current collector) using a doctor blade, and the thickness of the applied layer was adjusted to 100 μm. The electrodes were dried at 80 °C for 1 day and punched into circular electrodes with a diameter of 14 mm. A symmetric coin cell was constructed using a pair of circular electrodes (approximately 1.4 mg) and glass microfiber paper (18 mm diameter, grade GF / F) as a separator. The coin cell was fixed in a coin cell holder and its electrochemical properties were evaluated.

[0064] Referring to Figure 9A, the cyclic voltammetry responses of the electrodes are shown. YP-50F exhibits a conventional rectangular shape, which indicates theoretical capacitive behavior in the voltage window. However, the propylene-based ZTC exhibits a non-rectangular pattern and a broad, reversible peak at 0.2 V, which is attributed to the quinone-hydroquinone redox reaction. Hydroquinone is added to 1 M H2SO4 as a redox additive or mediator electrolyte. Hydroquinone directly participates in the electron transfer redox reaction. The performance of the supercapacitor is improved by their surface pseudocapacitive contribution at the electrode-electrolyte interface. During charging, hydroquinone acts as a 2H + and 2e - During discharge, the quinone is oxidized to quinone at the corresponding oxidation and reduction potentials, respectively. + 2e in - This redox property of hydroquinone mainly exhibits pseudocapacitance at the electrolyte-electrode interface, contributing to the increase in the total capacitance of the supercapacitor. The total pore volume of YP-50F (surface area 1665 m) 2 / g, total pore volume 0.66 cm 3 The larger ZTC (compared to the YP-50F capacitance of 103 F / g) can store more hydroquinone at the electrode-electrolyte interface and therefore has a higher capacitance. The propylene-based ZTC also showed a significantly higher capacitance of 209 F / g compared to the YP-50F capacitance of 103 F / g.

[0065] Referring to Figure 9B, the specific discharge capacity of the electrode as a function of current density is shown. High current densities, which result in fast discharge rates, require extremely fast ion transfer between the bulk electrolyte and the electrode surface. YP-50F retained only 58% of its initial capacitance at 15 A / g, while the propylene-based ZTC maintained 75% of its capacitance at the same rate. Without being bound by theory, it is believed that the improved performance can be attributed to uniform, three-dimensionally connected micropore channels that allow fast ion diffusion in the electrolyte.

Claims

1. 1. A method for producing zeolite-templated carbon (ZTC) for use as an active material in an electrode in a supercapacitor, comprising: providing CaX zeolite in a selected size; carbon deposition onto the CaX zeolite at elevated temperatures in a plug flow reactor using an organic precursor to produce a ZTC-zeolite composition; cooling the ZTC-zeolite composition; and heating the ZTC-zeolite composition by introducing a flow of inert gas for a specified time to produce a graphitized ZTC-zeolite composition, wherein the ZTC is heated to a graphitization temperature in the range of 820K to 1180K; cooling the graphitized ZTC-zeolite composition; and and washing the graphitized ZTC-zeolite composition with an acid to produce a prepared ZTC, the prepared ZTC having a selected surface area and operable for use as an active material in an electrode in a supercapacitor.

2. The method of claim 1 , wherein the inert gas stream comprises helium.

3. The method of any one of claims 1 to 2, wherein the inert gas stream comprises nitrogen.

4. The method of any one of claims 1 to 3, wherein the organic precursor is selected from the group consisting of propylene, ethanol, acetylene, and combinations thereof.

5. The method of any one of claims 1 to 3, wherein the organic precursor comprises propylene.

6. 6. The method of any one of claims 1 to 5, wherein the acid is selected from the group consisting of HCl, HF, and combinations thereof.

7. The method according to any one of claims 1 to 6, further comprising the step of drying the prepared ZTC.

8. 8. The method of any one of claims 1 to 7, wherein the prepared ZTC defines micropores in the range of 1.5 to 2 nm and mesopores in the range of 2 to 5 nm.

9. 9. The method of any one of claims 1 to 8, wherein the elevated temperature is in the range of 800K to 1080K.

10. an electrode comprising an active material and a metal component, the active material comprising zeolite-templated carbon (ZTC) produced by the method of claim 1; H ２ SO ４ an electrolyte comprising a membrane separator.

11. 11. The supercapacitor of claim 10, wherein the supercapacitor retains up to 75% of its capacitance at a high current density of 15 A / g.

12. The ZTC is 2500m ２ / g to 3000m ２ The supercapacitor of any one of claims 10 to 11, having a surface area of ​​1 / g.

13. The ZTC is 1.0 cm ３ 13. The supercapacitor of any one of claims 10 to 12, having a micropore density of more than 1000 .mu.m / g.

14. The supercapacitor of any one of claims 10 to 13, wherein the supercapacitor has a capacitance in the range of 100 to 250 F / g.

15. 1. A method for producing zeolite-templated carbon (ZTC) for use as an active material in an electrode in a supercapacitor, comprising: providing a NaX zeolite; NaX zeolite and CA ＋２ initiating ion exchange with ions to produce large crystal calcium (LCaX) zeolite; carbon deposition onto the LCaX zeolite using acetylene in a plug flow reactor at elevated temperature to produce a ZTC-zeolite composition; heating the ZTC by introducing a flow of inert gas for a specified time to produce a graphitized ZTC-zeolite composition, wherein the ZTC is heated to a graphitization temperature in the range of 820K to 1180K; cooling the graphitized ZTC-zeolite composition; and and washing the graphitized ZTC-zeolite composition with an acid to produce a prepared ZTC, the prepared ZTC having a selected surface area and operable for use as an active material in an electrode in a supercapacitor.

16. The method of claim 15 , wherein the inert gas flow comprises helium.

17. 17. The method of any one of claims 15 to 16, wherein the elevated temperature is in the range of 820K to 873K.

18. 18. The method of any one of claims 15 to 17, further comprising the step of performing a second carbon deposition on the graphitized ZTC-zeolite composition at an elevated temperature using acetylene.

19. 19. The method of any one of claims 15 to 16 or 18, wherein the elevated temperature is in the range of 800K to 873K.

20. 20. The method of any one of claims 15 to 19, wherein the acid is selected from the group consisting of HCl, HF, and combinations thereof.

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