Sustainable electrode materials from biomass and silica waste: a comprehensive electrochemical study for supercapacitor applications

Lithium-based batteries are today’s most favourable systems to provide energy for battery-powered applications such as (Hybrid) Electric Vehicles ((H)EVs), laptops and smartphones. Generally, (commercial) Li-ion batteries are two-electrode systems. Therefore, only the battery potential or impedance can be measured across the negative and positive electrode. However, for research purposes and to design more sophisticated Battery Management Systems (BMS) it is of interest to distinguish between both electrodes by using reference electrodes (RE), making it possible to measure the electrochemical characteristics of the individual electrodes. RE have already been introduced in many studies1,2. However, Electrochemical Impedance Spectroscopic (EIS) measurements on three-electrode Li-ion battery systems are prone to measurement artefacts. The majority of the research on EIS measurement artefacts focuses on the cell geometry and/or the position of the RE3,4. In the present contribution, new results are presented which show that EIS artefacts in the high frequency range can be compensated by averaging two distinctive EIS measurements. This strikingly results in artefact-free EIS measurements, especially in the high frequency range of the impedance spectra. This new method has been applied to pouch-type Li-ion batteries with integrated metallic lithium-based micro-reference electrodes1,2. Fig. 1 shows EIS measurements, revealing the high-frequency artefacts as well as the compensated EIS measurements. The EIS measurements of the battery (Bat), and those of the positive (P) and negative (N) electrode vs a lithium micro-reference electrode are shown in Fig. 1a. In addition, the impedance spectrum of the summation of P and N is shown (P+N), which obviously should end up with the same result as found for Bat in the entire frequency range. However, in the high frequency range a large deviation between Bat and P+N can be observed, indicating that the impedance measurements of the individual electrodes are not correct. This is because the generated excitation current induces a net voltage in the RE due to an unbalance in the measurement setup. Additional EIS measurements have been carried out with the measurement cables in a reversed connection. These results are shown in Fig. 1b and indicated with the subscript r. It can be observed that also these EIS measurements are deviating in the high frequency range but now in the opposite direction. However, averaging the measurements shown in Fig. 1a and b, results in correct impedance spectra for both the individual electrodes and added spectra, as indicated in Fig. 1c and, at a larger magnification, in Fig. 1d. It can indeed be seen that the impedance spectra of the individual electrodes are now artefact-free in the high frequency range and that the summation of P and N are now in perfect agreement with the total battery impedance in the entire frequency range. It can be concluded that high frequency impedance measurement artefacts observed with micro-reference electrodes integrated in Li-ion batteries can perfectly be compensated by averaging two EIS measurements. This results in artefact-free impedance spectra of (commercial) three-electrode batteries without making complicated measurement setups, which can easily be facilitated by conventional electronic circuitry as will be shown in the near future.

A green approach was employed for the synthesis Graphene-NiCo2O4 nanocomposite and its electrochemical property has been studied. The formation of phase and morphology was studied by diffraction and microscopic analysis. The prepared material was studied as an electrode material for supercapacitor application in a 2 M KOH electrolyte. In order to examine the electrochemical behavior of the prepared material cyclic voltammetry (CV), Galvanostatic charge- discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements were carried out in a 3-electrode system. Electrochemical studies revealed a high specific capacitance of 242 F g−1 and 165 F g−1 were obtained at a high scan rate of 10 mV s−1 and at an applied current density of 0.5 A g−1, respectively. A high initial capacitance retention value and coulombic efficiency of about 96% and 98% was retained after a long 1000 discharge cycles. Hence, the prepared material can be a potential candidate for high performance supercapacitor applications.

There exists a growing need for standardized On-Board Diagnostics (OBD) for electric vehicles [1] to provide accurate health metrics and guarantees to both consumers and manufacturers.Previous work has shown the powerful LIB capacity-based State-of-Health (SoH) estimation capability of Electrochemical Impedance Spectroscopy (EIS) measurements and data-driven models [2] [3]. Since EIS measurements are dependent not only on SoH but also State-of-Charge (SoC) and temperature [4], it is important that the measurements are conducted after the cell reaches an equilibrium, and that these other variables are also tracked. Although EIS measurements are somewhat quicker than some traditional capacity-determination experimental methods, the time taken for such measurements is not insignificant. Therefore, building a pipeline to determin the EIS frequency measurements most important for SoH estimation is an important task in developing a suitable EIS-based OBD. By exploring a frequency range between 0.1 and 200 Hz, we study EIS measurements related to diffusion and charge transfer processes in LIB operation [5], with each process being partially distinguishable due to their varying timescales.In this work, using EIS data collected from 5Ah LIBs with an NMC-111 cathode and a graphite anode at various SoCs (0, 25, 50, 75 and 100%) and cell lifetime (0, 10, 20, 40 and 90 days) as input features, we develop sequential, data-driven health estimation models for LIBs. The 22 cells used for this analysis have been aged over a period of 90 days in two different ways: either through active cycling at different C-rates (0.2 and 1C) and temperatures (0, 25 and 40⁰C), or passive “calendar aging” where the cells are left without use at a specific temperature and SOC. Using feature attribution techniques (Shapley values, feature occlusion, etc.), we find the most influential of the frequency ranges in the EIS measurements that relate strongly with cell performance degradation. To develop a streamlined and efficient SoH estimation framework, we formulate an optimization problem to find the EIS experimental design in terms of frequency ranges that delivers maximum accuracy in SoH estimation at different points in the lifetime of the cell. These streamlined and optimized EIS experimental designs and SoH estimation models can be used directly in the development of rapid and efficient on-board diagnostic tools.

In recent years, public awareness regarding the carbon dioxide emissions and the depletion of fossil fuel reserves has been increased. This motivates the development of the alternative energy sources based technology [1]. The Photoelectrochemical cell (PEC) is a capable clean and renewable way to convert sunlight into a storable chemical energy form. This technology enables the water to be split into hydrogen and oxygen by light-induced electrochemical processes [2]. One of the most studied and promising photocatalysts using in PEC is TiO2, which is relatively inexpensive and stable against photo irradiation while non-toxic [3]. In order to evaluate the PEC performances, the difference between various types of photocatalysts is usually attributed to the difference in their corresponding band gap energies, while the semiconductor particle size has not been taken into account as the main parameter. Having smaller particle size, particularly in the lower nanometer range, can give materials unique properties that could increase photoactivity [4]. There are some basic requirements for materials used as photo-electrodes such as optical function required to obtain maximal absorption of solar energy, the band gap of semiconductor which should be small enough to absorb a significant portion of the solar spectrum, the band edge potentials at the surfaces which must include the hydrogen and oxygen redox potentials, and especially sufficient charge transfer processes as well as the reaction kinetics at the semiconductor/electrolyte interface [5]. The present work reports the study of the kinetic aspects of photo electrochemical cells based on different nanoparticle sizes ranging from 50 nm down to 5 nm of TiO2, by using the electrochemical impedance spectroscopy (EIS) under illumination. The EIS is a useful method for the analysis of kinetic aspects such as charge transfer process that influences the cell performance. To measure the current response to the application of an AC voltage as a function of the frequency, EIS is considered as an electrochemical measurement [6]. Running the EIS is comparatively easy, but the interpretation of the results is often complicated and requires the application of suitable theoretical models. The equivalent electrical circuit is required to fit EIS data to identify the charge transfer phenomenon occurring in the PEC cell under 1 sun simulated illumination [5]. In our analysis, the three different electrode configurations were applied. The three semicircles are attributed to the redox reaction at the platinum counter electrode (Z1), the electron transfer at the TiO2 /electrolyte interface (Z2), and charge carrier transport in the electrolyte (Z3) (Figure 1a). The resistance elements R1, R2, and R3 are labeled as the real part of Z1, Z2, and Z3, respectively (Figure 1b). Therefore, it would be a powerful technique to recognize the internal resistance and the electron transportation of each photoelectrode in various particle size of the TiO2. A decrement of the internal resistance related to the electron transportation in the TiO2 /electrolyte interface causes an improvement in the electron transportation in the TiO2 thin film, which leads to the improvement of the cell efficiency. Furthermore, the exchange current density of each photoelectrode can be calculated when Rct (Charge Transfer Resistance) is known. This study is trying to reveal the effect of TiO2particle size on kinetic aspects of the Photoelectrochemical cell (PEC) for hydrogen production. Nanoparticle sizes ranging from 50 nm down to 5 nm were tested using EIS measurements. It was our prediction that by increasing particle size the internal resistance of electron transportation decreases, as per other literature [7]. The process of putting together the working electrode, as well as procedure and results of experiments, will be discussed.

In this study, 3 different materials were combined to form hybrid nanocomposite forSupercapBattery applications. The effects of using sulfur (S) doped and undoped reduced graphene oxide(S-rGO), Molybdenum (IV) sulfide (MoS2), and polyaniline (PANI) were used as a component ofnanocomposites. Electrochemical performances were performed by cyclic voltammetry (CV),galvanostatic charge / discharge (GCD) and electrochemical impedance spectroscopy (EIS)measurements. EIS measurements were analyzed by Nyquist, Bode-magnitude, Bode-phase, andAdmittance plots. Long-term stability tests were obtained by CV method using 1000 charge/dischargeperformances at a scan rate of 100 mV×s-1. The highest specific capacitance was calculated as Csp=1753.77 F×g-1at 2 mV×s-1for rGO/MoS2/PANI nanocomposite.

Study of oxygen diffusion in the cathode catalyst layer and gas diffusion layer for polymer electrolyte fuel cells with EIS

Thermal activation of impedance measurements on an epoxy coating for the corrosion protection: 2. electrochemical impedance spectroscopy study

Electrochemical and surface studies on the passivity of nitrogen and molybdenum containing laser cladded alloys in 3.5 wt% NaCl solution

This paper presents a method for an online real-time electrochemical impedance spectroscopy (EIS) measurement of batteries using closed-loop control of power converter. Unlike the previously proposed method which allows the measurement of the ac impedance for a single frequency, the presented method in this paper allows for obtaining the EIS for a spectrum of frequencies by using the information included in a single perturbation cycle, or a few cycles of perturbation to obtain a more accurate EIS with a very wide frequency range. This will result in faster EIS measurement for a spectrum of frequencies and under the same battery operating conditions. The presented method utilizes closed-loop control operation for the EIS measurement functionality, which allows for better control of the output voltage and for upgrading the concept to be able to achieve no added perturbation ripple at the output of the system. The presented online real-time EIS measurement method utilizes a power converter with closed-loop control in order to create an output voltage step-function perturbation at a given frequency to generate battery voltage and current responses. By applying Fourier analysis to these responses, an EIS can be obtained for a range of frequencies equal or higher than the perturbation frequency of the step function. In addition, this paper presents a method to eliminate the added perturbation ripple when two or more power converters are used. The theoretical basis and experimental prototype results are provided to illustrate and validate the presented method.

Enhancement of the photocurrent and electrochemical properties of the modified nanohybrid composite membrane of cellulose/graphene oxide with magnesium oxide nanoparticle (GO@CMC.MgO) for photocatalytic antifouling and supercapacitors applications

In recent years 3D printing is becoming popular among researchers for its reliability, cost-effective materials, and ease of use without having costly clean rooms. In this work we report the process of fabrication of an array patterned microfluidic device with its effect in Electrochemical impedance spectroscopy (EIS) and particle manipulator. With the optimized design of channel geometry and electrode pattern, this device can use in different lab-on-a-chip applications. A 3D printed microfluidic channel fabrication process is presented here along with a CAD drawing with microstructural dimension analysis. EIS is an expeditiously developing method used in characterizing materials and interfaces. By using equivalent circuits as models, it can determine the electrical properties of heterogeneous systems like membranes or electrolytes. For evaluating Impedance spectroscopy, a small amount of perturbing sinusoidal signal was applied to the electrochemical cell and measured the resulting current response. We take EIS measurements in three different electrolytes DI water (18.72μS/cm), tap water (666.12 μS/cm), and PBS 1 × (8235.24 μS/cm) with three different ranges of conductivity to observe their characteristics changes and to compare them. We analyze the electric double layer (EDL) effect for the electrode and electrolyte interface and how electron transfer kinetics and diffusional characteristics affect the spectra EIS is applicable to determine different electrochemical processes that can happen at the same time. Also, using AC electrokinetic (ACEK) flow the device can be used as a potential microfluid manipulator with its array electrode pattern. Both the micro-PIV and EIS experiments were done to verify the data validity of the microfluidics mixers.

All batteries degrade, but the challenge comes in quantifying that degradation and ultimately predicting a battery's failure and/or end-of-life. Battery health and monitoring have become more imperative with larger deployment of lithium batteries in electric vehicle (EV) and energy storage system (ESS) applications. Research shows a strong correlation between battery degradation and AC impedance measured using electrochemical impedance spectroscopy (EIS). This indicates that AC impedance can be used as a proxy for battery health. Additional information, like a battery's internal temperature can also be extracted from EIS measurements. As such, there is a strong push to measure AC impedance of a battery in field diagnostic applications. However, EIS is typically performed at rest under very stable environmental conditions. This traditional method of interpreting EIS must be modified to account for changing environmental conditions and changing current loads like those seen in EV and ESS applications. This paper explores the prospect of using EIS in a real-time battery management system (BMS) with the primary focus on determining the limits for interpreting EIS under loaded current conditions. An experiment is conducted to evaluate using EIS measurements taken on a loaded battery for the purpose of temperature estimation.A set of experiments were conducted where EIS was performed on Samsung 18650 Nickel Manganese Cobalt (NMC) cells while the cell was subject to loaded conditions. These experiments consisted of load currents ranging from charging rates (C-rate) between C/5 to 2C, and discharging rates (D-rate) between D/5 to 2D. Test were conducted at temperatures in the range of 5°C to 35°C. Closer inspection of Figure 1 shows EIS spectra diverging for charging conditions at lower frequencies. This is believed to be caused by a drift in the battery’s SOC. During charging, lower frequencies in AC impedance tend to have lower magnitude. Conversely, higher AC impedance magnitude is observed during discharging. The EIS frequency at which the loaded impedance deviates from the unloaded impedance by >10% is determined. The curve in Figure 2 represents the lowest EIS frequency at which under load EIS spectra is deemed usable, meaning that the shaded region below the curve represents the unusable portion of the EIS spectra. Moreover, this relationship serves as groundwork upon which to correct for EIS under loaded conditions. It is believed that the relationship of frequency limit as a function of load current shown in Figure 2 is slightly skewed by battery heating as an artifact of the test procedure. As a result, this experiment will be repeated prior to the final paper to gather data that accounts for these heating effects. A method to correct for shifts in an under-load EIS spectra will also be presented in the final paper.The prospect of using an under-load EIS spectra for internal temperature prediction is also demonstrated on a lab scale. In this experiment, the Samsung cell was soaked in a thermal chamber at constant temperature for several hours. A series of 3D discharge pulses are then applied to the battery for various durations. EIS is performed back-to-back during the current pulses (i.e., under load) and during rest times. The EIS spectra are fed into a cell temperature estimation model based on a non-zero interrupt frequency (NZIF) method. Figure 3 shows how EIS spectra changes with temperature for both loaded and unloaded conditions. The details of the NZIF model are beyond the scope of this paper. Thermistors are placed on the surface of the battery to measure a reference temperature. The results of the NZIF-predicted internal temperature are contrasted with measured thermistor battery surface temperatures, and those results are shown in Figure 4. These results indicate that NZIF-predicted internal temperature rises and falls during discharge and rest events, consistent with expected temperature rise and thermistor-measured battery surface temperature.Preliminary analysis suggests that constant current loads only slightly skew no-load EIS measurements, and that most of the EIS spectra taken under load is still usable. Furthermore, the usable portion of an EIS spectra can be determined by an EIS frequency vs load current relationship. This paper demonstrated that EIS can be used for internal temperature prediction while the battery is subject to a loaded condition, which is potentially useful to improve safety and performance of battery packs in field applications. In future work, more EIS measurements will be taken under different loaded conditions to improve NZIF predictions of internal temperature. Nevertheless, these early results are extremely promising for the use of EIS in real-time BMS applications. Figure 1

Performance of Biocarbon based Electrodes for Electrochemical Capacitor

Interconnected NiS nanosheets supported by nickel foam: Soaking fabrication and supercapacitors application

Electrochemical and optical study of BiPO4 nanostructures for energy storage applications