Application of zeolite template carbon (ZTC) as electrode of supercapacitor

Abstract

ZTC is used as an active material of a supercapacitor electrode. The ZTC is generated by a CaX template or a NaX template. And acetylene, ethanol or propylene is used for carbon vapor deposition. The ZTC-zeolite composition is graphitized, cooled, and subjected to acid pickling to remove the zeolite template. The ZTC produced by the method is characterized by having a high surface area and can be used as an active material in supercapacitors. The supercapacitor may also be characterized by having a H2SO4 electrolyte.

Description

Technical Field

[0001] The present disclosure relates to the application of zeolite template carbon (ZTC). In particular, disclosed herein are supercapacitor electrodes produced from ZTC and methods for producing ZTC. Background Art

[0002] Supercapacitors are electrochemical capacitors that store electrical energy. Compared to traditional batteries or conventional capacitors, supercapacitors are lighter, discharge faster, charge faster, have longer charge cycle life, and have excellent temperature performance. The performance of supercapacitors is related to many factors, including the choice of electrolyte and the composition of the electrode materials. The capacitance is proportional to the electrode surface area; therefore, electrochemically inert materials with high specific surface area are used. Conventional electrode materials include activated carbon, metal oxides, or graphite.

[0003] Conventional electrode materials lack uniform pores and channels, or have "dead pores" that hinder ion exchange. In addition, it is difficult to mass-produce traditional materials with consistency, and there are cases where production results are inconsistent. Therefore, there is a need for a material with high capacitance and large surface area for use as a supercapacitor electrode. Summary of the invention

[0004] Disclosed herein is a method for generating zeolite template carbon (ZTC) for use as an active material in a supercapacitor electrode. The method comprises the following steps: providing a CaX zeolite of a selected size; performing carbon vapor deposition on the CaX zeolite using an organic precursor in a plug flow reactor to generate a ZTC-zeolite composition. The carbon vapor deposition is performed at a high temperature. The method also includes the following: cooling the ZTC-zeolite composition; heating the ZTC-zeolite composition for a specified period of time by introducing an inert gas flow, wherein the ZTC is heated to a graphitization temperature in the range of 820K to 1180K to generate a graphitized ZTC-zeolite composition; cooling the graphitized ZTC-zeolite composition; and washing the graphitized ZTC-zeolite composition with an acid to generate the 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 flow is a helium gas flow containing helium. In some embodiments, the inert gas flow is a nitrogen gas flow containing nitrogen. The inert gas flow is heated.

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

[0006] The present invention also discloses a supercapacitor comprising an electrode, wherein the electrode comprises an active material and a metal component. The active material comprises a zeolite template carbon (ZTC) generated by the method claimed herein. The supercapacitor also comprises an electrolyte solution containing 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 surface area of ​​the ZTC is 2500 m 2 / g to 3000m 2 In some embodiments, the micropore density of ZTC is greater than 1.0 cm 3 In some embodiments, the capacitance of the supercapacitor is in the range of 100 F / g to 250 F / g.

[0008] The present invention also discloses a method for producing zeolite template carbon (ZTC), which is used as an active material in a supercapacitor electrode. The method comprises the following steps: providing NaX zeolite; initiating NaX zeolite and Ca +2 ions are ion exchanged to produce large crystalline calcium (LCaX) zeolite; and carbon vapor deposition is performed on the LCaX zeolite using acetylene in a plug flow reactor to produce a ZTC-zeolite composition. The carbon vapor deposition is performed at a high temperature. The method also includes the following: cooling the ZTC-zeolite composition; heating the ZTC-zeolite composition for a specified period of time by introducing an inert gas flow, wherein the ZTC is heated to a graphitization temperature in the range of 820K to 1180K 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 the prepared ZTC. The prepared ZTC can be used as an active material for an electrode in a supercapacitor and has a selected surface area. In some embodiments, the inert gas flow is a helium gas flow. The inert gas flow is heated.

[0009] In some embodiments, the high temperature is in the range of 820K to 873K. In some embodiments, the method further comprises the step of performing a second carbon vapor deposition on the graphitized ZTC-zeolite composition using acetylene. The second carbon vapor deposition is performed at high temperature. In some embodiments, the high temperature is in the range of 800K to 873K. In some embodiments, the acid is selected from the group consisting of HCl, HF, and combinations thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and other features, aspects and advantages of the present disclosure may be better understood in conjunction with the following description, claims and drawings. However, it should be noted that the drawings only illustrate several embodiments of the present disclosure and therefore should not be considered limiting of the scope as it may allow for other equally effective embodiments.

[0011] Figure 1 A simplified diagram of a supercapacitor.

[0012] Figure 2 1 is a graph of NH 3 temperature-programmed desorption of CaX and commercial NaX according to one embodiment.

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

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

[0015] Figure 5 is a graph of pore size distribution for a selected ZTC according to one embodiment.

[0016] Figure 6 FIG. 5 is a N 2 adsorption-desorption isotherm plot of a ZTC-zeolite composition for ZTC produced from LCaX according to one embodiment.

[0017] Fig. 7A is a graph of N2 adsorption-desorption isotherms of ZTC produced by LCaX according to one embodiment.

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

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

[0020] Fig. 8A 1 is a comparison chart of X-ray diffraction patterns of propylene-based ZTC according to one embodiment and commercially available activated carbon.

[0021] Figure 8B 1 is a comparison diagram of N2 adsorption-desorption isotherms of a propylene-based ZTC according to one embodiment and commercially available activated carbon.

[0022] Fig. 9A is a graph of cyclic voltammetric responses of an electrode comprising a propylene-based ZTC according to one embodiment and an electrode comprising commercially available activated carbon.

[0023] Fig. 9B is a graph comparing the specific discharge capacitance of a propylene-based ZTC according to one embodiment and a commercially available activated carbon as a function of current density. DETAILED DESCRIPTION

[0024] Although the present disclosure will be described by several embodiments, it should be understood that those skilled in the relevant art will recognize that many examples, variations and modifications of the described systems and methods are within the scope and spirit of the present disclosure. Therefore, the embodiments of the present disclosure described are set forth without loss of generality and without limiting the claims.

[0025] The terms "comprising," "including," "having," and the like used in conjunction with the embodiments of the present disclosure are synonymous and are each intended to have an open, non-restrictive meaning that does not exclude additional elements or steps. The term "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] Disclosed herein is a method for generating ZTC and a supercapacitor using ZTC as an electrode active material. The ZTC is generated using CaX zeolite as a template, and using carbon vapor deposition and various organic precursors. The specific capacitance of the supercapacitor using the ZTC as an electrode is twice as large as the specific capacitance of the supercapacitor using conventional electrodes. The supercapacitor disclosed herein can maintain 75% of the capacitance even at a high current density of 15A / g, which is better than conventional activated carbon electrodes. The resulting ZTC is characterized by having a large surface area, and in some embodiments, the surface area is greater than 3000m 2 / g. The ZTC may also have 1cm 3 / g or more large micropore volume. Advantageously, when the ZTC is used as an active material in a supercapacitor, the larger surface area and larger micropore volume provide more surfaces for ion and charge adsorption. Since ZTC has a high surface area available for reduction and oxidation, when used as an electrode material, it exhibits high ionic conductivity in addition to high electronic conductivity.

[0027] Supercapacitors are double-layer capacitors and are characterized by electrodes, electrolytes, and separators. Figure 1 , which depicts a simplified supercapacitor 100. The collector 102 collects ions with appropriate charges (positive charge on the positive side and negative charge on the negative side). The collector 102 is made of a material with high conductivity, low contact resistance with the electrode, and strong and stable bonding with the electrode. The collector 102 is also compatible with the electrolyte and will not corrode the collector 102 or react with the collector 102 in other ways when the system is running. The collector 102 can be made of aluminum foil, which conducts the current from the electrode. The aluminum foil also supports the electrode. The electrolyte 104 allows the charge to be transferred. In some embodiments, the electrolyte 104 is H2SO4. In some embodiments, hydroquinone is added to the electrolyte solution. The electrode 106 stores the charged particles on the electrode surface. In the embodiments disclosed herein, the electrode 106 is a ZTC generated using the method disclosed herein. The separator 108 physically separates the electrodes to prevent short circuits, but allows the charged ions to move while preventing conduction. The separator 108 is a relatively thin material, which can be a few hundredths of a millimeter, and is porous for conducting ions. The separator 108 is chemically inert to protect and maintain the stability and conductivity of the electrolyte. The separator 108 can be a membrane separator. Other materials suitable for the separator 108 can include open capacitor paper, non-woven porous polymer films containing materials such as polyacrylonitrile, woven glass fibers, porous woven ceramic fibers, or combinations thereof.

[0028] The electrode includes an active material and a metal collector, wherein the active material is characterized by a high surface area and the metal collector is characterized by a high conductivity. The metal collector may include a material similar to the collector 102. The energy storage of the supercapacitor depends on the physical adsorption of electrolyte ions on the surface of the carbon electrode, and the stored energy is proportional to the number of ions adsorbed on the electrode surface; therefore, electrodes using carbon materials (characterized by a high surface area) will produce high specific energy density / volume energy density. The uniform porosity with a three-dimensional interconnected microporous structure enables supercapacitors to have a significantly high power density due to the high ion transport rate within the microporous structure.

[0029] In embodiments disclosed herein, the electrode comprises ZTC as an active material. ZTC that can be used as a superconductor in embodiments described herein include those characterized by having both micropores and mesopores. In preferred embodiments disclosed herein, the ZTC is characterized by having essentially only micropores, which makes the pores of the ZTC mainly contained and concentrated in the micropore region. The diameter of the micropores is equal to or less than about 2 nanometers. The diameter of the mesopores is between about 2 nanometers and about 5 nanometers. The diameter of the macropores is greater than about 5 nanometers. In embodiments disclosed herein, the ZTC used as an active material in a supercapacitor is characterized by having an increased microporosity and consistent interconnected micropores, thereby improving the performance of the supercapacitor.

[0030] The ZTC disclosed herein is generated in a process using a zeolite as a template. A zeolite of a selected size is used as a template. The selected size may be in the form of a small crystal or a large crystal. The small crystal form may be in the range of 1 μm to 2 μm, and the large crystal form may be in the range of 10 μm to 20 μm. In some embodiments, NaX is a zeolite for 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 raise the temperature to a high temperature. The heated inert gas stream may be a He gas stream containing mainly helium, which may contain impurities that have substantially no effect on the process. The heated inert gas stream may be a nitrogen gas stream containing mainly nitrogen, which may contain impurities that have substantially no effect on the process. The heated inert gas stream heats the zeolite. Advantageously, helium or nitrogen provides an inert environment and can be used throughout the process to provide other advantages, such as further dehydrogenating the composition for graphitization. The elevated temperature may be in the range of 800 K to 1080 K, or 820 K to 1180 K, or 823 K to 873 K, or 823 K to 973 K, or 823 K to 1073 K, or 870 K to 1023 K, or 873 K to 973 K, or 873 K to 1023 K. In some embodiments, the elevated temperature is in the range of 970 K to 1000 K. In some embodiments, the elevated temperature is 823 K, or 873 K, or 973 K, or 1023 K, or 1073 K.

[0031] After the temperature of the zeolite has been raised and maintained for a period of time (in some embodiments, the time is 30 minutes), a stream containing one or more organic precursors is introduced into ZTC. The organic precursor can be heated. When passing through the bed, the temperature of the organic precursor reaches the same temperature as the zeolite. In some embodiments, the organic precursor includes 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 in the template by carbon vapor deposition in a plug flow reactor. The organic precursor forms a three-dimensional negative image of the zeolite template, interlaced between the channels of the zeolite, thereby generating a ZTC-zeolite composition. After a period of time, the organic precursor flow is stopped, and the temperature of the zeolite template is reduced to room temperature using a He gas flow. In some embodiments, the time of carbon vapor deposition is in the range of 2 hours to 9 hours, or 4 hours to 9 hours, or 4 hours to 5 hours. In some embodiments, the time of carbon vapor deposition is 2 hours, or 4 hours, or 5 hours, or 6 hours, or 9 hours.

[0032] In some embodiments, the ZTC-zeolite composition is further heated to graphitize the ZTC. The heating can be performed by a heated second inert gas stream, such as a heated helium gas stream or a heated nitrogen gas stream. The heated helium gas stream or nitrogen gas stream can also further dehydrogenate the ZTC-zeolite composition to graphitize it. The graphitization temperature may be in the range of 820K to 1180K, or 1100K to 1180K. In some embodiments, the graphitization temperature is 1123K. In some embodiments, the graphitization temperature is 1173K. In some embodiments, the graphitization time is 4 hours. In some embodiments, the graphitization time is in the range of 2 hours to 9 hours. The ZTC-zeolite composition is then cooled and washed with acid. The zeolite is dissolved by the acid, thereby retaining the ZTC. The ZTC-zeolite composition is acid-washed for 1 hour with HCl, HF, or a combination thereof, thereby removing the zeolite and generating 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 used as a zeolite to generate ZTC for use in supercapacitor electrodes. CaX is generated by ion-exchanging a commercial grade NaX zeolite. In some embodiments, a 10 m sample of NaX is added to a 200 mL 0.32 M Ca(NO3)2 solution and stirred for 4 hours. Commercial grade NaX zeolite is readily available and is not characterized by having large crystals or ultra-large crystal forms. In some embodiments, the generated CaX has small crystals that have been generated in the range of 1 μm to 2 μm.

[0034] Advantageously, the use of Ca +2The exchanged CaX can generate acidic sites in the zeolite, which catalyzes carbon deposition in the zeolite micropores and can achieve selective carbon deposition in the micropores. The generation of acidic sites is beneficial to improve the thermal stability of the zeolite template during the carbon vapor deposition step, thereby obtaining a more consistent ZTC product and a higher quality ZTC.

[0035] See also Figure 2 , which shows the NH3 temperature-programmed desorption curves of CaX and commercial NaX. CaX shows two desorption peaks at 473K and 653K. These two desorption peaks indicate the presence of two different types of acidic sites. NaX does not show desorption characteristics, so it has no acidic sites.

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

[0037] Table 1: Thermal stability of NaX zeolite and CaX zeolite

[0038] Zeolite <![CDATA[A z ]]> <![CDATA[T 起始 (K)]]> <![CDATA[T 0.5 (K)]]> NaX 1 933 1043 XC 0.93 983 1153

[0039] In Table 1, A z is the equivalent fraction of exchangeable cations in the zeolite; T 起始 is the temperature (in K) at which structural degradation is initially observed in the X-ray diffraction pattern; T 0.5 is the temperature (in K) at which 50% of the structure is decomposed. Advantageously, the enhanced stability of CaX at temperatures such as 973 K allows CaX zeolites to be used in higher temperature carbon vapor deposition processes.

[0040] In some embodiments, CaX can be prepared according to the process described herein, and can be used as a zeolite for generating multiple ZTCs. Propylene and ethanol can be used as organic precursors. In some embodiments, the organic precursor flow is propylene accounting for 2 volume % of an inert gas stream saturated with ethanol using a bubbler at 6kPa. In some embodiments, the organic precursor flow is acetylene accounting for 2 volume % of an inert gas stream. In other embodiments, a pure propylene stream or ethanol stream is used as an organic precursor. In some embodiments, the organic precursor may be propylene or ethanol, and its concentration in the inert gas stream may be 3 volume % to 5 volume %. In some embodiments, the organic precursor flow is propylene accounting for 2 volume % of a He gas stream saturated with ethanol using a bubbler at 6kPa. In some embodiments, the organic precursor flow is acetylene accounting for 2 volume % of a He gas stream. In other embodiments, a pure propylene stream or ethanol stream is used as an organic precursor. In some embodiments, the organic precursor may be propylene or ethanol, and its concentration in the helium gas stream may be 3 volume % to 5 volume %. In some embodiments, the organic precursor stream is propylene at 10% by volume in the N2 gas stream. The flow rate of the organic precursor may be 200 mL / min-g(沸石) .

[0041] In the carbon vapor deposition process, an organic precursor is used at a specified temperature and for a specified time, which time and temperature can vary. In some preferred embodiments, the specified temperature is in the range of 823K to 1073K; or, in the range of 823K to 873K; or, in the range of 1023K to 1073K. The specified temperature may be in the range of 800K to 1080K; or, in the range of 820K to 1180K; or, in the range of 823K to 873K; or, in the range of 823K to 973K; or, in the range of 823K to 1073K; or, in the range of 870K to 1023K; or, in the range of 873K to 973K; or, in the range of 873K to 1023K. In some embodiments, the specified temperature is in the range of 970K to 1000K. In some embodiments, the specified temperature is 823K, or 873K, or 973K, or 1023K, or 1073K. In some embodiments, the carbon vapor deposition time is in the range of 2 hours to 9 hours, or 4 hours to 9 hours, or 4 hours to 5 hours. In some embodiments, the carbon vapor deposition time is 2 hours, or 4 hours, or 5 hours, or 6 hours, or 9 hours. The ZTC-zeolite composition can be rinsed twice with a HCl-HF-water solution containing 3.4 wt % HCl and 3.3 wt % HF at room temperature for 1 hour. The material is filtered, washed and dried at a drying temperature. In some embodiments, the drying temperature is 373K. Embodiments of ZTC produced using the method disclosed herein are listed in Table 2 below.

[0042] Table 2: ZTC generated by CaX

[0043] ZTC Type Organic Precursors Carbon vapor deposition temperature (K) Carbon vapor deposition time (hours) CaX-973P5 Propylene 973 5 CaX-973E6 Ethanol 973 6 CaX-1073E6 Ethanol 1073 6 CaX-1023A2 Acetylene 1023 2

[0044] See also Figure 3 ,The X-ray diffraction pattern results of the selected ZTCs in Table 2 show a broad peak at 2θ = 5° to 6°, indicating the presence of structural order in the micropore arrangement. CaX-973P5 shows the highest resolution peak, indicating the most faithful replication of the CaX template.

[0045] See also Figure 4 , which depicts the N2 adsorption-desorption isotherms for selected ZTCs in Table 2. Figure 5 , which shows the pore size distribution of selected ZTCs in Table 2. Figure 4 and Figure 5It is shown that the ZTC has dual porosity, that is, it has both micropores with diameters ranging from 1.5 nm to 2 nm and mesopores with diameters ranging from 2 nm to 5 nm. The distribution was calculated using a non-local density functional theory algorithm. Table 3 below shows the Brunauer-Emmett-Teller (BET) surface area and pore volume (micropore volume, mesopore volume, total) of selected ZTCs:

[0046] Table 3: BET surface area and pore volume of ZTC

[0047] ZTC Type <![CDATA[S BET (m 2 / g)]]> <![CDATA[V 微孔 (cm 3 / g)]]> <![CDATA[V 中孔 (cm 3 / g)]]> <![CDATA[V 总和 (cm 3 / g)]]> CaX-973P5 1915 0.75 0.34 1.09 CaX-973E6 1596 0.58 0.48 1.06 CaX-1073E6 1826 0.65 0.66 1.31 CaX-1023A2 2567 0.95 0.42 1.37

[0048] In Table 3, V 微孔 (cm 3 / g) is calculated using the DR equation. The amount of mesopores present as shown in Table 3 is >0.40 cm 3 / g; and Figure 4 and Figure 5 This indicates that the microporous structure of CaX is not faithfully replicated in some areas, as CaX is characterized by having only micropores. This may be due to incomplete filling of the micropores of the zeolite structure by carbon. CaX-1023A2 in Table 3 uses an acetylene carbon precursor, and is characterized by having a higher surface area and the highest micropore volume compared to the other ZTCs produced. Without being bound by theory, it is believed that acetylene achieves the most faithful replication of the zeolite among the three organic precursors disclosed herein due to its small kinetic diameter.

[0049] In some embodiments, acetylene is used as a carbon precursor to generate ZTC with carbon vapor deposition using large crystal CaX (LCaX). LCaX can have a large grain size in the range of 10 μm to 20 μm. Advantageously, the use of LCaX can improve reproducibility and the ability to scale up production, and still have positive and consistent properties when using more than 1 g of zeolite, and have better commercial applications.

[0050] The high temperature during carbon vapor deposition of LCaX may be in the range of 800K to 1080K, or 820K to 1180K, or 823K to 873K, or 823K to 973K, or 823K to 1073K, or 870K to 1023K, or 873K to 973K, or 873K to 1023K. In some embodiments, the high temperature is in the range of 970K to 1000K. In some embodiments, the high temperature is 823K, or 873K, or 973K, or 1023K. In some embodiments, after carbon vapor deposition, the zeolite-ZTC composite is heat treated to graphitize. Graphitization may be performed using a rare gas. Graphitization may be performed using an inert gas. The rare gas may include helium. The inert gas may include nitrogen. The graphitization temperature may be less than or equal to 1123K. In some embodiments, the graphitization temperature is in the range of 1100K to 1180K. In some embodiments, the graphitization temperature is in the range of 820K to 1180K. In some embodiments, the graphitization temperature is in the range of 1123K to 1173K. In some embodiments, the graphitization temperature is 1123K. In some embodiments, the graphitization temperature is 1173K. In further embodiments, a second carbon vapor deposition may be performed, followed optionally by a second graphitization. The temperature of the second carbon vapor deposition and graphitization may be different or the same as the temperature of the first carbon vapor deposition and graphitization.

[0051] In some embodiments, two or more cycles of carbon vapor deposition are performed. In these embodiments, the ZTC-zeolite composition is cooled after the first carbon vapor deposition. The ZTC-zeolite composition is reheated and carbon vapor deposition is performed a second time. More cycles may be performed. After the carbon vapor deposition cycle is completed, the ZTC-zeolite composition is cooled and acid washed to produce ZTC.

[0052] Table 4 below discloses embodiments of ZTC produced from LCaX. These embodiments utilize acetylene as an organic precursor.

[0053] Table 4: ZTC generated by LCaX

[0054]

[0055] Table 5 below shows the Brunauer-Emmett-Teller (BET) surface area and pore volume (micropore volume, mesopore volume, total) of selected ZTCs produced from LCaX:

[0056] Table 5: BET surface area and pore volume of ZTC produced by LCaX

[0057] ZTC Type <![CDATA[S BET (m 2 / g)]]> <![CDATA[V 微孔 (cm 3 / g)]]> <![CDATA[V 中孔 (cm 3 / g)]]> <![CDATA[V 总和 (cm 3 / g)]]> LCaX-1023-2a 2567 0.95 0.42 1.37 LCaX-1023-2b 2156 0.83 0.43 1.26 LCaX-973-3 2381 0.93 0.31 1.24 LCaX-873-4 841 0.33 0.12 0.45 LCaX-873-4H 3049 1.12 0.45 1.57 LCaX-873-4H4Ha 2830 1.10 0.23 1.33 LCaX-873-4H4Hb 2840 1.12 0.21 1.33 LCaX-823-9H4H 2950 1.17 0.18 1.35

[0058] In Table 5, V 微孔 (cm 3 / g) is calculated using the DR equation. Table 5 shows that the higher the carbon vapor deposition temperature, the larger the surface area and the larger the micropore volume. Lower temperatures (such as the temperature 873K used in LCaX-873-4) will result in a lower surface area. On the contrary, thermal treatment will result in a larger surface area and a larger micropore volume. Without being bound by theory, it is believed that graphitizing the sample by thermal treatment can maintain a highly microporous structure so that the structure will not collapse after removing the zeolite. The data in Table 5 also show that carbon vapor deposition using acetylene is very sensitive to an increase in the initial amount of the zeolite template because the bed thickness increases. Therefore, compared with LCaX-1023-2a, the surface area and pore volume of LCaX-1023-2b have decreased, although their only difference is the different initial amounts of the zeolite templates used.

[0059] In some embodiments, ZTC is generated using sequential carbon synthesis. Advantageously, sequential carbon synthesis overcomes some of the scalability obstacles of the acetylene carbon vapor deposition disclosed above. In some embodiments, a first carbon vapor deposition of acetylene is performed at a first temperature, followed by graphitization at a graphitization temperature. The first temperature may be less than or equal to 873K. In some embodiments, the first temperature is in the range of 800K to 873K. In a preferred embodiment, the first temperature is in the range of 823K to 873K. The range of 823K to 873K can be considered to be the optimal temperature for initiating acetylene carbon vapor deposition, because the surface area obtained by the synthesis is increased and the micropore volume is larger. In other embodiments, the temperature may be in the range of 800K to 1080K, or 820K to 1180K, or 823K to 873K, or 823K to 973K, or 823K to 1073K, or 870K to 1023K, or 873K to 973K, or 873K to 1023K.

[0060] Graphitization may be performed using a rare gas. Graphitization may be performed using an inert gas. The rare gas may include helium. The inert gas may include nitrogen. The graphitization temperature may be less than or equal to 1123K. In some embodiments, the graphitization temperature is in the range of 1100K to 1180K. In some embodiments, the graphitization temperature is in the range of 820K to 1180K. In some embodiments, the graphitization temperature is in the range of 1123K to 1173K. In some embodiments, the graphitization temperature is 1123K. In some embodiments, the graphitization temperature is 1173K. In further embodiments, a second carbon vapor deposition may be performed, followed optionally by a second graphitization. The temperature of the second carbon vapor deposition and graphitization may be different from or the same as the temperature of the first carbon vapor deposition and graphitization.

[0061] Without wishing to be bound by theory, it is believed that acetylene deposition at a relatively low temperature (e.g., 873 K) results in uniform deposition of carbon throughout the zeolite bed, while heating the composition in an inert gas (e.g., helium) at 1123 K results in densification and graphitization of the carbon structure. This combination results in uniform and selective deposition of highly graphitized carbon within the zeolite micropores, resulting in high surface area and high micropore volume. Without wishing to be bound by theory, it is believed that incomplete filling of the zeolite template micropores results in the formation of mesopores in the ZTC.

[0062] See also Figure 6 , which shows the N2 adsorption-desorption isotherms for the ZTC-zeolite composition of ZTC generated by LCaX (before the zeolite template is removed by acid washing). The ZTC-zeolite composition of LCaX-873-4 exhibits negligible microporosity remaining inside the zeolite template, theoretically indicating that the zeolite micropores are completely filled with the ZTC carbon skeleton. The results of the ZTC-zeolite composition of LCaX-873-4H show that after heat treatment at 1123K for 4 hours to graphitize the carbon structure, about 25% of the zeolite micropore volume is regenerated, further indicating that the heat treatment densifies the ZTC carbon skeleton within the zeolite template micropores and shrinks the volume. Due to the regeneration of the zeolite micropore volume, it is advantageous to perform a second carbon vapor deposition, followed by an optional second graphitization. Figure 6 It shows that in the LCaX-873-4H4HZTC-zeolite composite, the micropores of the zeolite template are completely filled with the graphitized ZTC carbon skeleton. After acid washing, LCaX-873-4H4HZTC shows a decrease in mesopore volume while maintaining its surface area. As shown in Table 5 and Figure 6 As shown, a comparison of the properties of LCaX-873-4H4Ha with LCaX-873-4H4Hb demonstrates that sequential carbon synthesis allows the consistent reproduction of carbon structures in ZTCs regardless of the amount of zeolite used or the thickness of the zeolite bed in the reactor.

[0063] See also Fig. 7A , 7B and 7C, showing N2 adsorption isotherms and X-ray diffraction patterns for ZTC generated by LCaX, respectively. LCaX-873-4H4H appears to replicate the carbon structure most faithfully and exhibits a type I isotherm with a small amount of N2 adsorption in the high pressure region (P / P0>0.1). Compared with LCaX-873-4H4H, the total pore volume of LCaX-873-4H is higher, as indicated by the more significant adsorption when P / P0>0.1, which is due to the presence of secondary mesopores. LCaX-873-4H and LCaX-873-4H4H show a narrower and stronger pore size distribution in the micropore region (2nm). LCaX-873-4H4H shows a very sharp peak at 2θ=6.3° in X-ray diffraction, indicating that the replicated carbon has an ordered microporous structure like a zeolite template. Therefore, the presence or absence of a sharp X-ray diffraction peak at 2θ = 6.3° can be used as an indicator to determine whether the zeolite structure is faithfully reproduced and to judge the carbon deposition efficiency. Most importantly, the results of the isotherm and X-ray diffraction pattern of the ZTC generated by LCaX show that the pores are concentrated in the micropore region and have a sharp peak at less than about 2 nanometers.

[0064] Compared to conventional supercapacitors using activated carbon as electrode active materials, supercapacitors characterized by electrodes containing ZTC produced by the methods disclosed herein can show significant performance improvements. ZTC produced by carbon vapor deposition of a propylene organic vapor phase precursor can be used as an electrode active material. In some embodiments, the propylene organic vapor phase precursor is propylene at 10% of a N2 gas stream. In some embodiments, after carbon vapor deposition, the ZTC-zeolite composition is graphitized by a heat treatment as described herein.

[0065] An exemplary ZTC was synthesized by CaX and used as an electrode material using propylene accounting for 10% by volume of N2 gas flow as an organic precursor. The zeolite was continuously stirred using a bubbling fluidized bed reactor and rapid heat transfer was allowed during carbon vapor deposition. Beaded NaX zeolite was obtained from Shanghai Jiuzhou Chemical Company with a particle size distribution of 400 μm to 800 μm. For these samples, 250 grams of NaX zeolite were placed in a quartz tube with an inner diameter of 70 mm and a tube height of 1 m. At a nitrogen flow rate of 3 L / min, the temperature was raised to 973 K. The nitrogen flow rate was then changed to a flow rate of 2 L / min to 30 L / min, and the temperature was maintained for 15 minutes. Propylene and nitrogen were co-injected at a ratio of 3.2% by volume of propylene / N2. Some embodiments used propylene accounting for 10% by volume of nitrogen gas flow. After carbon vapor deposition with propylene, the ZTC-zeolite composition was graphitized by heat treatment at 1173 K. The reactor was heated at a heating rate of 2 K / min under a nitrogen flow rate of 2 L / min. The temperature was maintained for 3 hours to allow the deposited carbon skeleton to densify. 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.

[0066] The properties of the ZTC produced by the above process and used for supercapacitor electrodes are: surface area of ​​about 3056 m 2 / g, micropore volume is 1.12cm 3 / g, and the total pore volume is 1.72cm 3 / g.

[0067] The propylene-based ZTC was compared to an activated carbon commercially available from Kuraray Chemical under the name YP-50F. Fig. 8A and 8B , showing the X-ray diffraction patterns and N2 adsorption-desorption isotherms of propylene-based ZTC and YP-50F, respectively. Compared with YP-50F, the surface area of ​​propylene-based ZTC is much larger, 2700 m 2 / g, micropore volume is 0.99cm 3 / g, while the surface area of ​​YP-50F is 1665m 2 / g, micropore volume is 0.66cm 3 / g.

[0068] The capacitive performance of propylene-based ZTC was examined in comparison with that of YP-50F in capacitor applications. The ZTC was synthesized on a large scale using a 10 vol% propylene / nitrogen mixture in a bubbling fluidized bed reactor and the above process. A heat treatment at 1173 K for 3 h was performed to make the deposited carbon skeleton more graphitized. The resulting ZTC was labeled “ZTC-15L min -1 -1173K". The prepared ZTC was used as an electrode and tested. These results were compared with electrodes produced using commercially available activated carbon YP-50F (from Kuraray Chemical) as a reference material. Propylene-based ZTC and YP-50F were examined in 2032-type two-electrode button cells (from MTI) with a diameter of 20 mm and a height of 3.2 mm using 1 M H2SO4 electrolyte. The working electrode was prepared as follows: ZTC or YP-50F was mixed with a polyvinylidene fluoride (PVDF) binder and a commercially available carbon black (Super Carbon from TIMCAL Graphite & Carbon) ) were mixed in N-methyl-2-pyrrolidone (NMP). The weight ratio of active material: PVDF: carbon black was set to 7:1:2. The slurry was coated on a stainless steel foil (collector) using a scraper, and the coating thickness was adjusted to 100 μm. The electrode was dried at 80 ° C for 1 day and punched into a circular electrode with a diameter of 14 mm. A symmetric button cell was constructed using a pair of circular electrodes (about 1.4 mg) and a glass microfiber paper (18 mm in diameter, GF / F grade) as a separator. The prepared button cell was fixed on a button cell holder to evaluate the electrochemical performance.

[0069] See also Fig. 9A , which shows the cyclic voltammetric response of the electrode. YP-50F exhibits a regular rectangular shape, indicating a purely capacitive behavior within the voltage window. However, propylene-based ZTC exhibits a non-rectangular pattern and a broad reversible peak at 0.2 V, which can be attributed to the quinone-hydroquinone redox reaction. Hydroquinone is added to 1M H2SO4 as a redox additive or mediating electrolyte. Hydroquinone directly participates in the electron transfer redox reaction. The performance of the supercapacitor is improved by the surface pseudocapacitive contribution at the electrode-electrolyte interface. During charging, hydroquinone transfers 2H + and 2e - is oxidized to quinone; during the discharge process, quinone obtains 2e - and 2H +The redox property of hydroquinone mainly exhibits pseudocapacitance at the electrolyte-electrode interface and helps to increase the total capacitance of the supercapacitor. 2 / g, the total pore volume is 0.66cm 3 / g), the total pore volume of ZTC is larger, which can store more hydroquinone at the electrode-electrolyte interface, thus having a higher capacitance. Propylene-based ZTC also shows a significantly higher capacitance of 209 F / g compared to the capacitance of 103 F / g of YP-50F.

[0070] See also Fig. 9B , which shows the specific discharge capacitance as a function of the current density of the electrode. At high current densities resulting in fast discharge rates, the ion transfer between the bulk electrolyte and the electrode surface needs to be very fast. YP-50F only retained 58% of its initial capacitance at 15 A / g, while the propylene-based ZTC retained 75% of its capacitance at the same rate. Without being bound by theory, it is believed that the enhanced performance can be attributed to the uniform, three-dimensionally connected microporous channels, which allow for rapid ion diffusion of the electrolyte.

Claims

1. A method for producing a zeolite template carbon (ZTC) for use as an active material in an electrode of a supercapacitor, the method comprising the steps of: Providing a CaX zeolite of a selected size; performing carbon vapor deposition on a CaX zeolite using an organic precursor in a plug flow reactor to produce a ZTC-zeolite composition, wherein the carbon vapor deposition is performed at an elevated temperature; cooling the ZTC-zeolite composition; and then heating the ZTC-zeolite composition for a specified period of time by introducing an inert gas flow, 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; as well as The graphitized ZTC-zeolite composition is washed with an acid to produce a prepared ZTC having a selected surface area and capable of being used as an active material in an electrode of a supercapacitor.

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

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

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

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

10. A supercapacitor, comprising: An electrode comprising an active material and a metal component, wherein the active material comprises zeolite template carbon (ZTC) produced by the method of claim 1; an electrolyte comprising H2SO4; and Membrane separator.

11. The supercapacitor according to claim 10, wherein the supercapacitor maintains a maximum of 75% of capacitance at a high current density of 15 A / g.

12. The supercapacitor according to any one of claims 10 to 11, wherein the surface area of ​​the ZTC is 2500 m 2 / g to 3000m 2 / g range.

13. The supercapacitor according to any one of claims 10 to 12, wherein the ZTC has a value greater than 1.0 cm 3 / g micropore density.

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

15. A method of producing a zeolite template carbon (ZTC) for use as an active material in an electrode of a supercapacitor, the method comprising the steps of: Providing NaX zeolite; Initiation of NaX zeolite and Ca +2 ion exchange of ions to form large crystalline calcium (LCaX) zeolite; vapor deposition of carbon on LCaX zeolite using acetylene in a plug flow reactor to produce a ZTC-zeolite composition, wherein the vapor deposition of carbon is carried out at an elevated temperature; heating the ZTC for a specified period of time by introducing an inert gas flow, 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; as well as The graphitized ZTC-zeolite composition is washed with an acid to produce a prepared ZTC having a selected surface area and capable of being used as an active material in an electrode of a supercapacitor.

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

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

18. The method according to any one of claims 15 to 17, further comprising the steps of: The graphitized ZTC-zeolite composition is subjected to a second carbon vapor deposition using acetylene, wherein the second carbon vapor deposition is performed at the high temperature.

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. 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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