This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry &#38; Energy (MOTIE) of the Republic of Korea (No. 20214000000280), and the Chung-Ang University Graduate Research Scholarship 2021.

1. Fabrication of electrode and supercapacitor (Figure 1)
<ol>
	<li>Prepare the electrodes prior to the electrochemical analysis by combining 80 weight (wt)% of the electrode active material (0.8 g activated carbon), 10 wt% of the conductive material (0.1 g carbon black), and 10 wt% of the binder (0.1 g polytetrafluoroethylene (PTFE)).
	<ol>
		<li>Drop isopropanol (IPA; 0.1-0.2 mL) into the above-mentioned mixture, then spread the mixture thinly into a dough with a roller.</li>
	</ol>
	</li>
	<li>Before attaching the electrode to stainless steel (SUS) mesh, cut the SUS mesh to dimensions of 1.5 cm (width) &#215; 5 cm (length). After weighing the SUS mesh, coat the electrode (1 cm2) with a thickness of 0.1-0.2 mm on a SUS mesh and compress it with an electrode pressing machine. Here, the mass range of the electrode was 0.001-0.003 g.</li>
	<li>Dry the assembled supercapacitor electrode in an oven at 80 &#176;C for about 1 day to evaporate the IPA.</li>
	<li>Weigh the SUS mesh to obtain the weight of the electrode and then immerse the mesh in the electrolyte (2 M H2SO4 aqueous solution).</li>
	<li>Place the SUS mesh in a desiccator to remove air bubbles at the surface of the supercapacitor electrode.</li>
</ol>
2. Preparation of sequence file for electrochemical analysis
<ol>
	<li>CV sequence settings to obtain the analysis results.
	<ol>
		<li>Run the potentiostat measurement program to set the measurement experiment sequence file (Figure 2A).</li>
		<li>Click the Experiment button in the toolbar and go to Sequence File Editor &#62; New or click the New Sequence button (Figure 2B). Click the Add button to add a sequence step (Figure 3A).</li>
		<li>In every step, set Control as Sweep, Configuration as PSTAT, Mode as CYCLIC, and Range as Auto. Set the Reference for Initial(V) and Middle(V) as Eref and put -200e-3 in the Value. Set the Reference for Final(V) as Eref and put 800e-3 in the Value.</li>
		<li>The voltage scan rate is set as the desired value&#160;by&#160;the user. Here, the scan rate&#160;was&#160;set to 10&#160;mV/s. Put the value in Scanrate(V/s) as 10.0000e-3. Copy step-1 and click Paste[Dn] to paste it to step-2~5. Change the value of Scanrate(V/s) to either 20.000e-3, 30.000e-3, 50.000e-3, and 100.00e-3 respectively.</li>
		<li>Set Quiet time(s) as 0 and Segments as the number 2n+1 where n is the number of cycles. Here, 21 was applied for 10 cycles.</li>
		<li>Set Cut Off Condition as follows: for Condition-1 set Item as Step End and Go Next as Next.</li>
		<li>In the Controlling Miscellaneous Setting section, in the Sampling tab, set Item as Times(s), OP as &#62;=, and DeltaValue as 0.333333 (step-1), 0.166666 (step-2), 0.111111 (step-3), 0.06667 (step-4), and 0.03333&#160;(step-5) for each scan rate. This is the time interval for recording the data.</li>
		<li>Click Save As to save the CV analysis sequence file in any folder of the computer.</li>
	</ol>
	</li>
	<li>GCD sequence settings to obtain the analysis results
	<ol>
		<li>Run the potentiostat measurement program to set the measurement experiment sequence file (Figure 2A).</li>
		<li>Click the Experiment button in the toolbar and go to Sequence File Editor &#62; New or click the New Sequence button (Figure 2B). Click the Add button to add a sequence step (Figure 4A,B).</li>
		<li>In Step-1, set Control as CONSTANT, Configuration as GSTAT, Mode as NORMAL, and Range as Auto. Set the Reference for Current(A) as ZERO. When the mass of the electrode is 0.00235 g, set Value as 1.8618e-3 which means the current density is 1 A/g.</li>
		<li>Set Cut Off Condition as follow: for Condition-1 set Item as Voltage, OP as &#62;=, DeltaValue as 800e-3, and Go Next as Next.</li>
		<li>Set the following in the Controlling Miscellaneous setting section: in the Sampling tab, set Item as Times(s), OP as &#62;=, and DeltaValue as 0.1.</li>
		<li>In Step-2, each set is the same as in Step-1, except set value of Current(A) as the negative value of Step-1 (-1.8618e-3). Set Condition-1 as follows: Item as Voltage, OP as &#60;=, DeltaValue as -200e-3, and Go Next as Next.</li>
		<li>In Step-3, set Control as LOOP, Configuration as CYCLE, and set List-1 in Condition-1 of Cut Off Condition as Loop Next, Go Next as Step-1, and set List-2 as Step End, and Go Next as Next. Set the Iteration value as 10 which is the number of repeating cycles.</li>
		<li>Step-1, step-2, and step-3 form a single loop. Copy and paste them after step-4 and change the value of Current (A) to either 3.7236e-3, 5.5855e-3, 9.3091e-3, or 18.618e-3, calculated for various current densities of 2,3,5, and 10 A/g.</li>
		<li>Click Save As to save the GCD analysis sequence file in any folder of the computer.</li>
	</ol>
	</li>
	<li>EIS sequence settings to obtain the analysis results
	<ol>
		<li>Run the potentiostat measurement program to set the measurement experiment sequence file (Figure 2A).</li>
		<li>Click the Experiment button in the toolbar and go to Sequence File Editor &#62; New or click the New Sequence button (Figure 2B). Click the Add button to add a sequence step (Figure 5A,B).</li>
		<li>In Step-1, set Control as CONSTANT, Configuration as PSTAT, Mode as TIMER STOP, and Range as Auto. Set the Reference for Voltage(V) as Eref and Value as 500e-3 which is half of the size of the voltage range.</li>
		<li>Set cut-off condition as follows: for Condition-1 set Item as Step Time, OP as &#62;=, DeltaValue as 3:00, and Go Next as Next. This is the process for stabilizing the potentiostat device.</li>
		<li>In Step-2, set Control as EIS, Configuration as PSTAT, Mode as LOG, and Range as Auto. Set Speed of Initial (Hz) as Normal and value of Initial (Hz) and Middle (Hz) as 1.0000e+6 which is the high-frequency value and Final (Hz) as 10.000e-6, which is the low-frequency value.</li>
		<li>Set the Reference for Bias(V) as Eref and Value as 500e-3. To get a linear response result, set the amplitude (Vrms) as 10.000e-3. Set Density as 10 and Iteration as 1.</li>
		<li>Click Save as to save the EIS analysis sequence file in any folder of the computer.</li>
	</ol>
	</li>
</ol>
3. Electrochemical analysis
<ol>
	<li>Operate the potentiostat device and run the measurement program to perform the CV, GCD, and EIS analyses. Fill 100 mL of 2 M H2SO4 aqueous electrolyte in a glass container (a beaker-shaped glass container was used).</li>
	<li>Before starting the measurement, in the potentiostat, connect the three types of lines: the working electrode (L-WE), the reference electrode (L-RE), and the counter electrode (L-CE), to the SUS mesh, reference electrode (Ag/AgCl), and counter electrode (Pt wire), respectively (Figure 6). Connect the fourth line, the working sensor (L-WS) to the L-WE.</li>
	<li>Cover the glass container with a cap, and immerse the three electrodes in the electrolyte through a perforation in the cap. Position the electrodes so that the WE is maintained at a constant distance between the CE and RE.</li>
	<li>Run the measurement program and open the prepared sequence. Click Apply to CH to insert the sequence to the potentiostat&#39;s channel. Start the measurement by clicking the Start button.</li>
</ol>
4. Data analysis
<ol>
	<li>CV data analysis for fitting the graph
	<ol>
		<li>Open raw measurement data in the convert program to obtain the results in spreadsheet format. Click the File button and open the raw data. Select all cycles and click Export ASCII on the toolbar. Check the Cycle, Voltage, and Current in Columns to Export on the right side of the program.</li>
		<li>Click Create Directory and then click Export to convert raw data to spreadsheet format.</li>
		<li>Open the spreadsheet file and extract the voltage and current values of cycles 10, 20, 30, 40, and 50, which are the last cycles at each scan rate.</li>
		<li>Plot the CV graph with the voltage as the X-axis and specific current density as the Y-axis.</li>
	</ol>
	</li>
	<li>GCD data analysis for fitting the graph
	<ol>
		<li>Open raw measurement data in the convert program to obtain the results in spreadsheet format. Click the File button and open the raw data. Select all cycles and click Export ASCII on the toolbar. Check the Cycle, Voltage, and CycleTime in Columns to Export on the right side of the program.</li>
		<li>Click Create Directory and then click Export to convert raw data to spreadsheet format.</li>
		<li>Open the spreadsheet file and extract the voltage and CycleTime values for cycles 10, 20, 30, 40, and 50, which are the last cycles at each current density.</li>
		<li>Plot the GCD graph with the cycle time as the X-axis and voltage as the Y-axis.</li>
	</ol>
	</li>
	<li>EIS data analysis for fitting the graph
	<ol>
		<li>Open raw measurement data in EIS program. Click the Open file icon and open raw data and click the file name that was applied to see the detailed data.</li>
		<li>Extract Z&#39; [Ohm] as the X value and Z&#39;&#39; [Ohm] as the Y value and plot the EIS graph.</li>
	</ol>
	 </li>
</ol>

The authors have nothing to disclose.

This study provides a protocol for various analyses using a three-electrode system with a potentiostat device. This system is widely used to evaluate the electrochemical performance of supercapacitors. A suitable sequence for each analysis (CV, GCD, and EIS) is important for obtaining optimized electrochemical data. Compared with the two-electrode system having a simple setup, the three-electrode system is specialized for analyzing supercapacitors at the material level15. However, the selection of appropriate experimental parameters such as the electrolyte42, potential range43, scan rate14, and current density14 is important for obtaining high-quality data. The parameters that must be judiciously set are summarized below.
The weight ratio may vary depending on the type of material used. The ratio can be adjusted according to the properties of the conductive material and binder used. The best ratio must maximize the amount of active material while maintaining the electrical conductivity and mechanical strength of the electrode. An 80 wt% ratio of the active material is widely used44,45,46,47.
The potential range is dependent on the electrochemical stability window (ESW) of the electrolyte. The ESW of an electrolyte can be determined by its reduction and oxidation potentials, which define the stable range within which the electrolyte can be used without decomposition48,49. The potential window for aqueous electrolytes is usually below 1.23 V, which is restricted by the thermodynamic potential of water electrolysis50. In the case of organic electrolytes, the potential window depends on the organic solvent used; organic electrolytes have a high voltage window (2.6 to 4.0 V)51. Researchers should set the optimal potential range in sequence according to the chosen electrolyte. In the case of an electrolyte that reacts upon contact with air, the container must be sealed.
The scan rate is the potential that varies linearly with the scan speed18 and has a crucial effect on the voltammetric behavior of materials. The optimal scan rate range cannot be specified because it depends on the material. At a higher scan rate, more redox reactions occur, and if the redox reaction is too fast, it is difficult to measure the electrochemical properties of the materials. At a lower scan rate, some peaks may be missing because there is sufficient time for activation during the redox reaction14. Researchers can select and adjust the optimal range using reference and empirical data. A scan rate from 50 mV/s to 1 V/s is commonly used. The current density is another parameter that affects the electrochemical parameters, including the capacitance14. If the current density is too high, the operating voltage is hardly measured. It is one of the reasons that the capacitance and energy density is decreased. An appropriate current density can be determined from the CV graph. The range of the y-axis shown for each scan rate may be used as the current density. A repeated cycle is applied in CV and GCD analyses to obtain the steady-state data. The cycle required to reach the steady state differs depending on the properties of the material. During cycling, the system attempts to achieve the equilibrium state and struggles to reach the same pattern14. Selecting a sufficient number of cycles for the materials is important. Ten cycles were applied in the present experiment.
Each parameter must be carefully determined because each parameter influences the next parameter value. Selecting the parameter values for obtaining optimal electrochemical data may involve modifying variables based on the initial experimental results. Evaluation of the electrochemical performance of a supercapacitor using the three-electrode system provides reliable data based on the values that the researcher has entered, but it is solely up to the user to set suitable parameters for analysis. The protocols specified in this report and the explanations supporting them will aid researchers in making a more informed decision.
To evaluate the electrochemical performance of supercapacitors, the mixing ratio of the electrode material and the electrode weight are vital parameters in the final step. The specific capacitance and current density can be obtained from the exact loading amount of the active material using the weight information. Inaccurate weight information may cause errors in the results. Finally, the installation of the appropriate equipment is important. The respective electrodes should not come into contact, but the distance between each electrode is indicated by the resistance of the system. Therefore, the electrodes should be placed as close as possible29. It is necessary to minimize external factors that may affect the evaluation of the supercapacitor by determining whether the electrode connection parts are corroded, or if the RE and the CE are in good condition.
The three-electrode system can perform detailed analysis, but through this, all performance of the supercapacitor cannot be evaluated. As mentioned earlier, the three-electrode system analyzes only one electrode at the material level. The final supercapacitor system consists of symmetrical or asymmetric electrodes and requires further evaluation of this system for application to real-life and industry. Many studies have conducted an evaluation using a three-electrode and two-electrode system together52,53,54,55. The system is also changing depending on the application. Not just evaluating supercapacitor, it is widely used in fuel cells56,57 and surface treatment58,59 fields. Various changes are taking place, such as giving flexibility60 or deviating from the existing form to another form61. The materials&#39; characteristics can be easily evaluated with this system. Therefore, it will be applied in various forms to fields that require material analysis and evaluation.
In this paper, a supercapacitor was fabricated according to the proposed protocol. In addition, we evaluated the performance of a supercapacitor at the material level using various electrochemical analyses by utilizing the three-electrode system. The electrochemical properties of the electrodes were determined by adjusting the sequence parameters. This basic electrochemical protocol using the three-electrode system can be used to guide manufacturing and evaluation techniques for supercapacitor testing for beginners in this field of research.

Supercapacitors have attracted enormous attention as suitable power sources for a variety of applications such as microelectronic devices, electric vehicles (EVs), and stationary energy storage systems. In EV applications, supercapacitors can be used for rapid acceleration and can enable the storage of regenerative energy during the deceleration and braking processes. In renewable energy fields, such as solar power generation1 and wind power generation2, supercapacitors can be used as stationary energy storage systems3,4. Renewable energy generation is limited by the fluctuating and intermittent nature of these energy supplies; therefore, an energy storage system that can respond immediately during irregular power generation is required5. Supercapacitors, which store energy via mechanisms that differ from those of lithium-ion batteries, exhibit a high power density, stable cycle performance, and fast charging-discharging6. Depending on the storage mechanism, supercapacitors can be distinguished into double-layer capacitors (EDLCs) and pseudocapacitors7. EDLCs accumulate electrostatic charge at the electrode surface. Therefore, the capacitance is determined by the amount of charge, which is affected by the surface area and porous structure of the electrode materials. By contrast, pseudocapacitors, which consist of conducting polymers and metal oxide materials, store charge through a Faradaic reaction process. The various electrochemical properties of supercapacitors are related to the electrode materials, and developing new electrode materials is the main issue in improving the performance of supercapacitors8. Hence, evaluating the electrochemical properties of these new materials or systems is important in the progress of research and further applications in real life. In this regard, electrochemical evaluation using a three-electrode system is the most basic and widely utilized method in lab-scale research of energy storage systems9,10,11,12,13.
The three-electrode system is a simple and reliable approach for evaluating the electrochemical properties, such as the specific capacitance, resistance, conductivity, and cycle life of supercapacitors14. The system offers the benefit of enabling analysis of the electrochemical characteristics of single materials15, which is in contrast to the two-electrode system, where the characteristics can be studied through the analysis of the given material. The two-electrode system just gives information about the reaction between two electrodes. It is suitable for analyzing the electrochemical properties of the entire energy storage system. The potential of the electrode is not fixed. Therefore, it is not known at what voltage the reaction takes place. However, three-electrode system analyzes only one electrode with fixing potential which can perform a detailed analysis of the single electrode. Therefore, the system is targeted toward analyzing the specific performance at the material level. The three-electrode system consists of a working electrode (WE), reference electrode (RE), and counter electrode (CE)16,17. The WE is the target of research, assessment as it performs the electrochemical reaction of interest18 and is composed of a redox material that is of potential interest. In the case of EDLCs, utilizing high surface area materials is the main issue. Therefore, porous materials with a high surface area and micropores, such as porous carbon, graphene, and nanotubes, are preferred19,20. Activated carbon is the most common material for EDLCs because of its high specific area (&#62;1000 m2/g) and many micropores. Pseudocapacitors are fabricated with materials that can undergo a Faradaic reaction21. Metal oxides (RuOx, MnOx, etc.) and conducting polymers (PANI, PPy, etc.) are commonly used22. The RE and CE are used to analyze the electrochemical properties of the WE. The RE serves as a reference for measuring and controlling the potential of the system; the normal hydrogen electrode (NHE) and Ag/AgCl (saturated KCl) are generally chosen as the RE23. The CE is paired with the WE and completes the electrical circuit to allow charge transfer. For the CE, electrochemically inert materials are used, such as platinum (Pt) and gold (Au)24. All components of the three-electrode system are connected to a potentiostat device, which controls the potential of the entire circuit.
Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) are typical analytical methods that use a three-electrode system. Various electrochemical characteristics of supercapacitors can be assessed using these methods. CV is the basic electrochemical method used to investigate the electrochemical behavior (electron transfer coefficient, reversible or irreversible, etc.) and capacitive properties of material during repeated redox processes14,24. The CV plot shows redox peaks related to the reduction and oxidation of the material. Through this information, researchers can evaluate the electrode performance and determine the potential where the material is reduced and oxidized. Furthermore, through CV analysis, it is possible to determine the amount of charge that material or electrode can store. The total charge is a function of the potential, and the capacitance can be easily calculated6,18. Capacitance is the main issue in supercapacitors. A higher capacitance represents the ability to store more charge. EDLCs give rise to rectangular CV patterns with linear lines so that the capacitance of the electrode can be calculated easily. Pseudocapacitors present redox peaks in rectangular plots. Based on this information, researchers can assess the electrochemical properties of materials using CV measurements18.
GCD is a commonly employed method for identifying the cycle stability of an electrode. For long-term use, the cycle stability should be verified at a constant current density. Each cycle consists of charge-discharge steps14. Researchers can determine the cycle stability through variations in the charge-discharge graph, specific capacitance retention, and Coulombic efficiency. EDLCs give rise to a linear pattern; thus, the specific capacitance of the electrode can be calculated easily using the slope of the discharge curve6. However, pseudocapacitors exhibit a nonlinear pattern. The discharge slope varies during the discharging process7. Furthermore, the internal resistance can be analyzed through the current-resistance (IR) drop, which is the potential drop owing to the resistance6,25.
EIS is a useful method for identifying the impedance of energy storage systems without destruction of the sample26. The impedance can be calculated by applying a sinusoidal voltage and determining the phase angle14. The impedance is also a function of the frequency. Therefore, the EIS spectrum is acquired over a range of frequencies. At high frequencies, kinetic factors such as the internal resistance and charge transfer are operative24,27. At low frequencies, the diffusion factor and Warburg impedance can be detected, which are related to mass transfer and thermodynamics24,27. EIS is a powerful tool for analyzing the kinetic and thermodynamic properties of a material at the same time28. This study describes the analysis protocols for evaluating the electrochemical performance of supercapacitors using a three-electrode system.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Activated carbon</td>
			<td>GS</td>
			<td></td>
			<td>Active material</td>
		</tr>
		<tr>
			<td>Ag/AgCl electrode</td>
			<td>BASi</td>
			<td>RE-5B</td>
			<td>Reference electrode</td>
		</tr>
		<tr>
			<td>Carbon black</td>
			<td>Hyundai</td>
			<td></td>
			<td>Conductive material</td>
		</tr>
		<tr>
			<td>Desicator</td>
			<td>Navimro</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode pressing machine</td>
			<td>Rotech</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Extractor</td>
			<td>WonA Tech</td>
			<td></td>
			<td>Convert program (raw data to excel form)</td>
		</tr>
		<tr>
			<td>Isopropanol(IPA)</td>
			<td>Samchun</td>
			<td>I0346</td>
			<td>Solvent to melt the binder</td>
		</tr>
		<tr>
			<td>Polytetrafluoroethylene(PTFE)</td>
			<td>Hyundai</td>
			<td></td>
			<td>Binder</td>
		</tr>
		<tr>
			<td>Potentiostat</td>
			<td>WonA Tech</td>
			<td>Zive SP1</td>
			<td></td>
		</tr>
		<tr>
			<td>Pt electrode</td>
			<td>BASi</td>
			<td>MW-018122017</td>
			<td>Counter electrode</td>
		</tr>
		<tr>
			<td>Reaction flask</td>
			<td>Duran</td>
			<td></td>
			<td>Container for electrolyte</td>
		</tr>
		<tr>
			<td>SM6</td>
			<td>WonA Tech</td>
			<td></td>
			<td>Program of setting sequence and measuring electrochemical result</td>
		</tr>
		<tr>
			<td>Sulfuric acid</td>
			<td>Samshun</td>
			<td>S1423</td>
			<td>Electrolyte</td>
		</tr>
		<tr>
			<td>SUS mesh</td>
			<td>Navimro</td>
			<td></td>
			<td>Current collector</td>
		</tr>
		<tr>
			<td>Teflon cap</td>
			<td>WonA Tech</td>
			<td></td>
			<td>Cap of the electrolyte continer</td>
		</tr>
		<tr>
			<td>Zman</td>
			<td>WonA Tech</td>
			<td></td>
			<td>EIS program</td>
		</tr>
	</tbody>
</table>

evaluating the electrochemical properties of supercapacitors using the three-electrode system

The three-electrode system is a basic and general analytical platform for investigating the electrochemical performance and characteristics of energy storage systems at the material level. Supercapacitors are one of the most important emergent energy storage systems developed in the past decade. Here, the electrochemical performance of a supercapacitor was evaluated using a three-electrode system with a potentiostat device. The three-electrode system consisted of a working electrode (WE), reference electrode (RE), and counter electrode (CE). The WE is the electrode where the potential is controlled and the current is measured, and it is the target of research. The RE acts as a reference for measuring and controlling the potential of the system, and the CE is used to complete the closed circuit to enable electrochemical measurements. This system provides accurate analytical results for evaluating electrochemical parameters such as the specific capacitance, stability, and impedance through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Several experimental design protocols are proposed by controlling the parameter values of the sequence when using a three-electrode system with a potentiostat device to evaluate the electrochemical performance of supercapacitors. Through these protocols, the researcher can set up a three-electrode system to obtain reasonable electrochemical results for assessing the performance of supercapacitors.

The electrodes were manufactured according to protocol step 1 (Figure 1). Thin and homogeneous electrodes were attached to SUS mesh with a size of 1 cm2 and 0.1-0.2 mm thickness. After drying, the weight of the pure electrode was obtained. The electrode was immersed in a 2 M H2SO4 aqueous electrolyte, and the electrolyte was allowed to sufficiently permeate the electrode before the electrochemical analyses. The production sequence and system setting for the electrochemical measurements were performed according to protocol steps 2 and 3 (Figure 2 - Figure 5). The glass container used in the system can have various shapes29 where the distance between each electrode is minimized. The measurement results were organized and interpreted according to protocol step 4. To confirm whether the analysis was successful, the real-time graph obtained during the analysis and the shape of the graph of the raw data obtained after the analysis should be checked (Figures 3B,4C,5C). In the case of CV, a box-shaped graph was obtained at 300 mV/s, whereas GCD showed a symmetrical triangle. In the case of EIS, it is possible to check whether the analysis is properly performed through the size of the equivalent series resistance and semicircle, and the pattern at a low frequency depending on the material characteristics.
Figure 7 presents the CV, GCD, and EIS data. CV is the most common technique for determining the capacitance of electrodes and the characteristics of materials as a function of the potential. The well-developed rectangle-shaped CV graph in the scan rate range from 10 to 200 mV/s indicates EDLC characteristics and confirms that the supercapacitor operated well as an EDLC with good rate capability30 (Figure 7A). However, when the scan rate was above 300 mV/s, the graph lost its rectangular shape and collapsed, which means that the electrode lost the EDLC characteristics (Figure 7B). The specific capacitance of supercapacitors can be calculated from the CV data at each scan rate using the following equation6:
<img alt="Equation 1" src="/files/ftp_upload/63319/63319eq01.jpg" />&#160; (1)
where Csp, v, V1, V2, and I(V) are the specific capacitance, scan rate, discharge voltage limit, charge voltage limit, and voltammogram current density (A/g), respectively. The specific capacitance was 126, 109, 104, 97, and 87 F/g at respective scan rates of 10, 20, 30, 50, and 100 mV/s.
GCD can be used to determine the cycle stability and resistance parameters of the electrode. As shown in Figure 7C, the GCD graph of the electrode presented a symmetric linear profile31 in all current densities within the potential range from &#8722;0.2 to 0.8 V. This is also a characteristic property of EDLCs. Subsequently, as the current density increased, the time on the x-axis decreased, and the area of the triangle decreased. The specific capacitance was calculated by dividing the discharge time by the voltage and multiplying by the current density, giving values of 153, 140, 135, 120, and 110 F/g at the respective current densities of 1, 2, 3, 5, and 10 A/g. The internal resistance (RESR) was calculated using the following equation32:
<img alt="Equation 2" src="/files/ftp_upload/63319/63319eq02.jpg" />&#160; &#160; (2)
where &#916;V is the IR drop, which is the potential drop due to the resistance (this is an additive effect of the cell components and electrolytes6,25), and I is the current density. The value of RESR was 0.00565 &#8486; at a current density of 1 A/g. The long-cycle test can be used to determine the cycle stability of the WE. The cycle stability is one of the main issues in energy storage systems when applied to an electrical device and can be confirmed by repeating many cycles at a constant current density. As shown in Figure 7D, the AC WE showed 99.2% capacitance retention over 10000 cycles at a current density of 10 A/g.
The EIS graphs are plotted in Figure 7E,F. EIS is a useful method for identifying the resistance of cell systems without destruction. The impedance of the cell is a function of the frequency (the typical frequency range is from 100 kHz to 10 MHz) with a small voltage (5 mV or 10 mV)14,33. In addition, the Nyquist plot is a common way to represent the impedance data, where the imaginary/real part of the impedance is plotted in the frequency range. The resulting data are recorded from the high-frequency domain to the low-frequency domain, and each part represents various types of resistance6. As shown in Figure 7E, the Nyquist plot can be divided into four parts. Part A corresponds to the equivalent series resistance, which is known as the sum of the resistance of the bulk electrolyte34,35 and the contact resistance between the electrode and the current collector36,37. Part B presents a semicircle, the diameter of which reflects the electrolyte resistance in the pores of the electrodes38 or charge transfer resistance34. Furthermore, the sum of parts A and B can be interpreted as the internal resistance, which is the sum of the bulk electrolyte resistance and the charge transfer resistance36. In part C, the 45&#176; line region indicates the ion transport limitation of the electrode structures in the electrolyte34,39 or ion transport limitation in the bulk electrolyte35. Lastly, the vertical line in part D (Figure 7F) is attributed to the dominant capacitive behavior of the electric double layer formed at the electrode/electrolyte interface40. The EIS graph for the example system showed very small equivalent series resistance and semicircle (Rct) values, and the shape at low frequencies appeared close to vertical, which indicates the EDLC characteristics of the device6,41.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63319/63319fig01.jpg" /> 
Figure 1. Fabricating process of supercapacitor. (A) Prepare the materials for electrode and mix with IPA. (B) Make an electrode in the form of a dough. (C) Spread the electrode thinly, cut it into 1 cm2 size with a thickness of 0.1-0.2 mm, and attach it to the stainless steel (SUS) mesh. (D) Immerse the supercapacitor in electrolyte after pressing and drying. Abbreviations: PTFE= polytetrafluoroethylene; IPA= isopropanol. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63319/63319fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63319/63319fig02.jpg" /> 
Figure 2. Run the program for sequence settings. (A) Run the analysis program and (B) create the new sequence file with the editor. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63319/63319fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/63319/63319fig03.jpg" /> 
Figure 3. CV sequence settings. (A) CV sequence setting for each scan rate and (B) real-time measurement CV graphs. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63319/63319fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/63319/63319fig04v2.jpg" /> 
Figure 4. GCD sequence settings. (A, B) GCD sequence setting for each current density and (C) real-time measurement GCD graphs. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63319/63319fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/63319/63319fig05.jpg" /> 
Figure 5. EIS sequence settings. (A, B) EIS sequence setting and (C) real-time measurement EIS graph. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63319/63319fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/63319/63319fig06v2.jpg" /> 
Figure 6. The basic composition of the three-electrode system for electrochemical measurement. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63319/63319fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/63319/63319fig07.jpg" /> 
Figure 7. Electrochemical analyses graphs. (A) CV at low scan rates (10 mV/s - 100 mV/s); (B) CV at high scan rates (200 mV/s - 1000 mV/s); (C) GCD at a current density from 1 to 10 A/g; (D) Long cycle test at the current density of 10 A/g; (E, F) EIS Nyquist plots. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/63319/63319fig07large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Evaluating the Electrochemical Properties of Supercapacitors using the Three-Electrode System at JoVE.com

Evaluating the Electrochemical Properties of Supercapacitors using the Three-Electrode System

The protocol describes the evaluation of various electrochemical properties of supercapacitors using a three-electrode system with a potentiostat device.

The three-electrode system is a basic and general analytical platform for investigating the electrochemical performance and characteristics of energy ...

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11.5K 조회수.  Chung-Ang University. The protocol describes the evaluation of various electrochemical properties of supercapacitors using a three-electrode system with a potentiostat device.

비디오: Evaluating the Electrochemical Properties of Supercapacitors using the Three-Electrode System

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

Fabrication of VB2/Air Cells for Electrochemical Testing

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

VB의 제작<sub&gt; 2</sub전기 테스트를위한&gt; / 공기 전지

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for ...

연구

공학

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.
In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

유기 화합물을 사용하여 실리콘 표면과 나노 와이어의 단층 연락 도핑

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction.

Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape.

Disordered structures offer new mechanisms for forming photonic bandgaps and unprecedented freedom in functional-defect designs. To circumvent the computational challenges of disordered systems, we construct modular macroscopic samples of the new class of PBG materials and use microwaves to characterize their scale-invariant photonic properties, in an easy and inexpensive manner.

무질서 광 밴드 갭 (photonic bandgap) 재료의 광자 속성을 연구에 전자 레인지 및 유전체 고체의 육안 샘플을 사용하여

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). ...

Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents and hence higher efficiencies. Photon up-conversion by way of triplet-triplet annihilation (TTA-UC) is an attractive technique for using these otherwise wasted low energy photons to produce photocurrent, while not interfering with the photoanodic performance in a deleterious manner. Further to this, TTA-UC has a number of features, distinct from other reported photon up-conversion technologies, which renders it particularly suitable for coupling with DSC technology. In this work, a proven high performance TTA-UC system, comprising a palladium porphyrin sensitizer and rubrene emitter, is combined with a high performance DSC (utilizing the organic dye D149) in an integrated device. The device shows an enhanced response to sub-bandgap light over the absorption range of the TTA-UC sub-unit resulting in the highest figure of merit for up-conversion assisted DSC performance to date.

An integrated device, incorporating a dye-sensitized solar cell and triplet-triplet annihilation up-conversion unit was produced, affording enhanced light harvesting, from a wider section of the solar spectrum. Under modest irradiation levels a significantly enhanced response to low energy photons was demonstrated, yielding a record figure of merit for dye-sensitized solar cells.

삼중 항 - 삼중 종말 최대 변환 시스템을 통합하면 하위 밴드 갭 빛에 염료 감응 형 태양 전지의 응답을 향상시키기 위해

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents ...

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

A protocol is presented for the synthesis and preparation of nanoparticles consisting of electroactive polymers.

전기 활성 고분자 나노 입자 출전 광열 등록

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Plasmatron에서 절제 재료 시험 중에 방출 분광 경계 계층 조사

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Uncoupling Coriolis Force and Rotating Buoyancy Effects on Full-Field Heat Transfer Properties of a Rotating Channel

An experimental method for exploring the heat transfer characteristics of an axially rotating channel is proposed. The governing flow parameters that characterize the transport phenomena in a rotating channel are identified via the parametric analysis of the momentum and energy equations referring to a rotating frame of reference. Based on these dimensionless flow equations, an experimental strategy that links the design of the test module, the experimental program and the data analysis is formulated with the attempt to reveal the isolated Coriolis-force and buoyancy effects on heat transfer performances. The effects of Coriolis force and rotating buoyancy are illustrated using the selective results measured from rotating channels with various geometries. While the Coriolis-force and rotating-buoyancy impacts share several common features among the various rotating channels, the unique heat transfer signatures are found in association with the flow direction, the channel shape and the arrangement of heat transfer enhancement devices. Regardless of the flow configurations of the rotating channels, the presented experimental method enables the development of physically consistent heat transfer correlations that permit the evaluation of isolated and interdependent Coriolis-force and rotating-buoyancy effects on the heat transfer properties of rotating channels.

Here, we present an experimental method for decoupling the interdependent Coriolis-force and rotating-buoyancy effects on full-field heat transfer distributions of a rotating channel.

An experimental method for exploring the heat transfer characteristics of an axially rotating channel is proposed. The governing flow parameters that ...

Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and subsequent safety issues becomes increasingly important. In a Li-ion cell setup, the voltage measurement across the positive and negative terminals inherently includes the effect of the cathode and anode which are coupled and sum to the total cell performance. Accordingly, the ability to monitor the degradation aspects associated with a specific electrode is extremely difficult because the electrodes are fundamentally coupled. A three-electrode setup can overcome this problem. By introducing a third (reference) electrode, the influence of each electrode can be decoupled, and the electrochemical properties can be measured independently. The reference electrode (RE) must have a stable potential that can then be calibrated against a known reference, for example, lithium metal. The three-electrode cell can be used to run electrochemical tests such as cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Three-electrode cell EIS measurements can elucidate the contribution of individual electrode impedance to the full cell. In addition, monitoring the anode potential allows the detection of electrodeposition due to lithium plating, which can cause safety concerns. This is especially important for the fast charging of Li-ion batteries in electric vehicles. In order to monitor and characterize the safety and degradation aspects of an electrochemical cell, a three-electrode setup can prove invaluable. This paper aims to provide a guide to constructing a three-electrode coin cell setup using the 2032-coin cell architecture, which is easy to produce, reliable, and cost-effective.

Three-electrode cells are useful in studying the electrochemistry of lithium-ion batteries. Such an electrochemical setup allows the phenomena associated with the cathode and anode to be decoupled and examined independently. Here, we present a guide for construction and use of a three-electrode coin cell with emphasis on lithium plating analytics.

3 전극 동전 전지 준비 및 Electrodeposition 리튬-이온 배터리에 대 한 분석

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and ...

Evaluating Targeting Accuracy in the Focal Plane for an Ultrasound-guided High-intensity Focused Ultrasound Phased-array System

Phased arrays are increasingly used as high-intensity focused ultrasound (HIFU) transducers in the existing extracorporeal ultrasound-guided HIFU (USgHIFU) systems. The HIFU transducers in such systems are usually spherical in shape with a central hole where a US imaging probe is mounted and can be rotated. The image on the plane of treatment can be reconstructed through the image sequence acquired during the rotation of the probe. Therefore, the treatment plan can be made on the reconstructed images. In order to evaluate the targeting accuracy in the focal plane of such systems, the protocol of a method using a bovine muscle and marker-embedded phantom is described. In the phantom, four solid balls at the corners of a square resin model serve as the reference markers in the reconstructed image. The target should be moved so that both its center and the center of the square model can coincide according to their relative positions in the reconstructed image. Swine muscle with a thickness of about 30 mm is placed above the phantom to mimic the beam path in clinical settings. After sonication, the treatment plane in the phantom is scanned and the boundary of the associated lesion is extracted from the scanned image. The targeting accuracy can be evaluated by measuring the distance between the centers of target and lesion, as well as three derivative parameters. This method cannot only evaluate the targeting accuracy of the target consisting of multiple focal spots rather than a single focal spot in a clinically relevant beam path of the USgHIFU phased-array system, but it can be also used in the preclinical evaluation or regular maintenance of USgHIFU systems configured with phased-array or self-focused HIFU transducer.

This study describes a protocol to evaluate the targeting accuracy in the focal plane of an ultrasound-guided high-intensity focused ultrasound phased-array system.

초음파 위상 어레이 시스템에 초점을 맞춘 초점면에 타겟팅 정확도 초음파 유도 높은 강도 대 한 평가

Phased arrays are increasingly used as high-intensity focused ultrasound (HIFU) transducers in the existing extracorporeal ultrasound-guided HIFU ...

Operation of the Collaborative Composite Manufacturing (CCM) System

The automated tape placement and the automated fiber placement (AFP) machines provide a safer working environment and reduce the labor intensity of workers than the traditional manual fiber placement does. Thus, the production accuracy, repeatability and efficiency of composite manufacturing are significantly improved. However, the current AFP systems can only produce the composite components with large open surface or simple revolution parts, which cannot meet the growing interest in small complex or closed structures from industry.
In this research, by employing a 1-degree of freedom (DoF) rotational stage, a 6-RSS parallel robot, and a 6-DoF serial robot, the dexterity of the AFP system can be significantly improved for manufacturing complex composite parts. The rotational stage mounted on the parallel robot is utilized to hold the mandrel and the serial robot carries the placement head to mimic two human hands that have enough dexterity to lay the fiber to the mandrel with complex contour.
Although the CCM system increases the flexibility of composite manufacturing, it is quite time-consuming or even impossible to generate the feasible off-line path, which ensures uniform lay-up of subsequent fibers considering the constraints like singularities, collisions between the fiber placement head and mandrel, smooth fiber direction change and keeping the fiber placement head along the norm of the part&#39;s surface, etc. Moreover, due to the existing positioning error of the robots, the on-line path correction is needed. Therefore, the on-line pose correction algorithm is proposed to correct the paths of both parallel and serial robots, and to keep the relative path between the two robots unchanged through the visual feedback when the constraint or singularity problems in the off-line path planning occur. The experimental results demonstrate the designed CCM system can fulfill the movement needed for manufacturing a composite structure with Y-shape.

Operation of the Collaborative Composite Manufacturing CCM System

A collaborative composite manufacturing system is developed for robotic lay-up of composite laminates using the prepreg tape. The proposed system allows the production of composite laminates with high levels of geometrical complexity. The issues in the path planning, coordination of the robots and control are addressed in the proposed method.

협업 복합제조(CCM) 시스템 운영

The automated tape placement and the automated fiber placement (AFP) machines provide a safer working environment and reduce the labor intensity of ...