Charge-discharge Measurements Research Articles

Porous activated carbon electrodes derived from Eleusine coracana biowaste in electric double layer capacitors: Nanoarchitectonics and performance

The development of high-performance supercapacitors from biowaste is crucial for advancing sustainable and renewable energy storage technologies. In this study, we report the fabrication of electrodes for high-performance supercapacitors using porous carbon derived from red millet (Eleusine coracana) straw. Porous carbon was synthesized via a two-step chemical activation process using KOH, resulting in a hierarchical pore structure comprising macro-, meso-, and micropores. The red millet-based porous carbon electrodes, assembled in a two-electrode symmetrical supercapacitor, exhibited a specific capacitance of 68 Fg⁻1 at a current density of 0.5 Ag⁻1 in a 1 M Na₂SO₄ aqueous electrolyte. At a mass loading of 5 mg per electrode, the system demonstrated a specific capacitance of 300 Fg⁻1 at 1 Ag⁻1, with an energy density of 9.1 Whkg⁻1 and a power density of 1.86 kWkg⁻1, as determined from galvanostatic charge-discharge measurements. Additionally, the supercapacitor showed excellent cyclic stability, retaining 98.78% of its initial capacitance after 5000 cycles at 10 Ag⁻1. These findings highlight the potential of porous carbon derived from agricultural biowaste for scalable applications in electric double-layer capacitors.

Electrochemical boost via thermally reduced graphene oxide for tailoring composite paste electrodes

Carbon-based composite materials are employed in diverse electrochemical applications, such as in catalysis, (bio)molecular sensing, and energy storage. In practice, electrode material needs to be highly conductive to allow high-speed electron transference to electrolyte species and possess high-surface area to obtain greater measured signals and power capabilities, as well as long useful life and stability. In this sense, graphene derivatives emerge as interesting candidates, even more so if they constitute part of practical, economical and versatile paste electrodes.This work presents a detailed analysis of the electrochemical performance of paste electrodes fabricated with multilayer partially reduced graphene oxide (rGO). The rGO was strategically produced via thermal treatment as a key factor that minimizes both mass loss and energy consumption. The results obtained through diffraction, microscopy and spectroscopy techniques show an effective partial reduction in the range of 100 to 400 °C. Furthermore, the enhanced electrochemical performance of rGO was determined by exploring the specific capacitance from cyclic voltammetry (CV) and galvanostatic charge–discharge measurements (GCD) as well as charge transfer resistance via electrochemical impedance spectroscopy (EIS). Our results evidence how an integral performance with suitable chemical, structural and morphological properties achieved for GO heat-treated at 200 °C leads to an improved electronic conductivity when a small part is combined with graphite in paste electrodes. This latter combination provides higher versatility compared to other alternatives since it arises as an economical and effective carbonaceous matrix for (bio)electrochemical sensors, hybrid supercapacitors or other desired nanotechnological applications.

Pemanfaatan Limbah Ban Bekas untuk Sintesis Nanokomposit MnO2/C dengan Metode Hidrotermal sebagai Material Superkapasitor

Activated carbon from waste tires is used as MnO2 metal oxide doping in making MnO2/C-based nanocomposites into high-density and environmentally friendly supercapacitor electrodes. The MnO2/C nanocomposite synthesis process was carried out using the hydrothermal method by varying the mass of activated carbon by 1.25 g, 2.5 g and 3.75 g to determine the optimum results. Based on the results of research that has been carried out, it shows that MnO2/C can be used as a high density supercapacitor electrode. This is in accordance with the XRD test results which show that the MnO2 nanocomposite with the addition of C was successfully synthesized and has an orthorhombic crystalline phase. The SEM test results show that the material has almost the same morphology, namely many protrusions which make each particle have high roughness. The most optimal results were obtained from the MnO2/C-50 variation because it has the highest C element content, namely 39.93%, so it has the highest capacitance value of 5.791 f/g during the CV test. The GCD test shows that electrodes with a carbon variation of 2.5 g have a much longer and constant charge-discharge measurement time. In the EIS test, this variation shows a resistance value that is not too high and not too small, materials that have good storage capacity or capacity have moderate resistance.

Electrochemical performance of graphene oxide synthesized from graphitic spent potlining for energy storage application

The hazardous nature of spent pot lining (SPL) generated from aluminum smelters poses environmental challenges due to its high fluoride and cyanide content. However, techniques and recent studies have shown that SPL can be converted into valuable carbon-based materials through innovative recycling with potential applications in energy storage devices. This work presents an electrochemical performance evaluation of graphene oxide (GO) electrodes derived from acid-treated SPL for supercapacitor applications. The SPL-derived graphene oxide (SPL-GO) was synthesized via a facile and scalable improved Tour method. SPL-GO electrodes were fabricated by drip-coating SPL-GO/PVDF/DMF suspension on nickel foams. The morphology, structure, and chemical composition of the SPL-GO were characterized using advanced techniques such as energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), Fourier transforms infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The electrochemical properties of the SPL-GO in 3 M KOH were characterized with a three-electrode system using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements. The results demonstrate that SPL-GO exhibits a relatively high specific capacitance of 762.90 F/g at 1 A/g with corresponding power and energy densities of 502 W/kg and 106.60 Wh/kg, respectively. Additionally, excellent cycling stability of 85.4 % was achieved after 10,000 cycles with a coulombic efficiency of 95.23 %. These results suggest a superior rate capability of SPL-GO, rendering it a viable candidate for supercapacitor applications. Furthermore, this work sets the foundation for the sustainable use of industrial waste in energy storage devices, suggesting a novel, eco-friendly material for practical supercapacitor applications.

Marigold flower-like structured battery-type Cu2O/Co(OH)2 composite electrode material for high-performance supercapacitors

Addressing the limitations of individual Cu2O and Co(OH)2 components, this study aims to develop a high-performance supercapacitor electrode by synergistically combining these materials. A composite electrode material of Cu2O/Co(OH)2 was effectively synthesized on nickel foam via a facile hydrothermal method for supercapacitor applications. The as-fabricated Cu2O/Co(OH)2 composite electrode exhibits a hierarchical marigold flower-like morphology that comprises of many interspersed nanoflakes. This unique morphology offers several advantages, including increased surface area, abundant electroactive sites, and enhanced electrolyte accessibility, all of which contribute to superior electrochemical performance. The Cu2O/Co(OH)2 electrode demonstrates exceptional battery-type supercapacitor behavior, characterized by prominent redox peaks in cyclic voltammetry curves and a well-defined potential plateau during galvanostatic charge-discharge measurements. The electrode delivers an outstanding specific capacitance of 90.21 mA h g⁻1 at a current density of 1.25 A g⁻1 and retains a remarkable 81.91 % capacitance at a high current density of 12.5 A g⁻1. Furthermore, the electrode exhibits impressive cycling stability, maintaining approximately 107.84 % of its initial specific capacity value after 200 cycles at 7.5 A g⁻1. Electrochemical impedance spectroscopy measurements reveal low solution resistance and charge-transfer resistance, signifying efficient charge-transfer kinetics within the electrode. These findings highlight the potential of Cu2O/Co(OH)2 composite electrodes as promising candidates for high-performance supercapacitor applications.

Electrochemical measurements, structural and morphological studies of electrodeposited polypyrrole supercapacitor electrode

This study presented the electrochemical deposition of potassium nitrate-doped polypyrrole (Ppy:KNO3) on stainless steel (SS), graphite sheet (GRs), and carbon fiber (CF) substrates, Ppy:KNO3/SS, Ppy:KNO3/GRs, and Ppy:KNO3/CF supercapacitor electrodes. Structural, morphological, and molecular analyses were conducted using X-ray diffraction (XRD), scanning electronic microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). SEM images exhibited distinct morphologies of Ppy:KNO3 films, varying with cycles, scan rates, and Ppy:KNO3 concentrations. Ppy:KNO3/CF film displayed a unique structure with minimal particle aggregation. Electrochemical performance was assessed through Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) measurements and electrochemical impedance spectroscopy (EIS). Notably, Ppy:KNO3/CF demonstrated a specific capacitance of 1020 F/g at 1 A/g. It exhibited 92 % capacitance retention after 1000 cycles, along with impressive power and energy densities of 310 W/kg and 71.2 Wh/kg, respectively. These results represented a significant progress in the development of high-performance, durable supercapacitors.

Unveiling the Mn3+/ Mn4+ and Ni2+ potential as a high-capacity material for next-generation energy storage devices

In this study, we synthesized MnOx nanowires via hydrothermal methods and explored the impact of nickel (Ni) doping on their morphology and electrochemical properties. We investigated the structural and chemical changes induced by Ni incorporation by utilizing TEM and XPS analyses. Our results revealed that Ni doping influenced the distribution of manganese oxidation states, with 1.6 wt% Ni-doped nanowires exhibiting the optimized condition. Also, we observed a balance between the Mn3+/Mn4+ ratio with the Ni doping. Electrochemical characterization demonstrated enhanced capacity in Ni-MnOx nanowires at the 1.6 wt% Ni doping level. Galvanostatic charge-discharge measurements confirmed the superior performance of this level of Ni doping; moreover, the fabrication of asymmetric supercapacitor cells using these nanowires showed improved energy storage capabilities. The main results showed exceptionally high capacity (955.55 and 383.33 mAh g−1 at 1 and 20 A g−1, respectively) and an excellent rate capability. Cycling stability tests over 8500 cycles demonstrated excellent retention of capacity, underscoring the durability of the optimized Ni-MnOx nanowires, with a retention of 85 % of its initial capacity. Thus, this study emphasizes the significance of Ni doping in MnOx nanowires for enhancing electrochemical performance when the synthetic process is controlled, offering valuable insights for high-performance energy storage device development.

Utilization of NiO-rGO Nanoarchitectures-Based Composite Electrodes for High-Performance Electrochemical Applications

The urge to transition from fossil fuels to sustainable energy solutions has driven the exploration of advanced energy conversion and storage technologies. In this context, supercapacitors have garnered substantial interest for their high cyclic life span and power density. This study presents the facile synthesis of NiO and NiO/rGO composites (NO-I, NO-II, and NO-III) for battery-type applications, with a focus on their structural, morphological, and electrochemical characterizations. The results indicate the successful fabrication of crystalline materials with notable porosity in NO-III. Electrochemical analysis reveals battery-type behavior, with an inverse relationship between specific capacity (Q) and scan rates. Galvanostatic charge-discharge (GCD) measurements highlight enhanced charge storage capability, particularly in NO-III. GCD results showed the maximum values for (Q = 288 Cg−1), energy density (E = 36.12 Wh kg−1), and power density (P = 3.06 kW h−1) at 1.7 Ag−1 for NO-III, underscoring its potential for advanced energy storage systems.

Enhanced electrochemical validation of metal organic frameworks-derived TiO2/Fe-TiO2 as an active electrode for supercapacitors

Developing supercapacitor materials that are both efficient and durable, with high cycle life and specific energy, poses a significant challenge due to issues in electrodes such as volume expansion and electrode degradation that occur over time. This work reports a simple, novel, and cost-effective synthesis method to fabricate high surface area “Iron (Fe) doped TiO2 materials” via the metal-organic framework (MOF) route for supercapacitor application. Morphological analysis revealed a disc-like shaped pattern for pristine TiO2 (PT), and a cuboid form for Fe-doped TiO2 (FeT). The electrochemical investigation of MOF-derived PT and FeT electrode materials demonstrated the superior performance of FeT. Cyclic Voltammetry revealed enhanced electrochemical properties in FeT. Galvanostatic charge-discharge measurements confirmed FeT’s higher energy storage capacity, reaching a maximum specific capacitance of 925 Fg− 1. Long-term cycling tests exhibited excellent stability, with FeT retaining 67% of its initial capacitance after 6000 cycles and showing prolonged self-discharge. Overall, the results underscore the potential of Fe-doped TiO2 for high-performance supercapacitors.

Impact of carbon dots on the structural, morphological, magnetic, and electrochemical performance of Zn ferrite for energy storage applications

Magnetic core-shell Zn ferrite and carbon dots (C-dots) composite have been synthesized in this work using a simple coprecipitation and hydrothermal process, respectively. X-ray diffraction (XRD) patterns demonstrate an inverse spinel structure of Zn ferrites; the lattice parameter has decreased from 8.19 Å to 8.10 Å with C-dots. Scanning electron microscopy (SEM) images reveal rods-like structures for C-dots, and in the composite case, it is uniformly dispersed using low contrast consecutive C-dot layers to produce a core-shell structure. Zn ferrites are non-uniform in size, whereas C-dots and their composites are in uniform shape according to SEM images. The energy dispersive X-ray (EDX) study indicates that the substitution has been successful. For Zn ferrites, and composite, the Fourier transform infrared (FTIR) spectra shows that the absorption band of the tetrahedral site at 990 cm−1, and 870 cm−1, respectively. Different bonds in the infrared spectrum match specific function groups and bonding in various chemicals. The vibrating sample magnetometry (VSM) results indicates that the composite displays ferrimagnetic behavior. The specific capacity for composite has been found to be 2351 and 1790 F/g using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements, respectively. Higher electrochemical performance of the prepared composites may be helpful for energy storage systems.

Facile synthesis, enhanced annealing-structural investigation and supercapacitive potentials of NiFe2O4 spinel nanopowder

Herein, we examined and optimized the influence of annealing temperature on microstructural and electrochemical charge storage properties of spinel NiFe2O4 nanopowder synthesized from a simple one-pot sol-gel route. Microstructural techniques encompassing Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, x-ray diffractometry, and Fourier transform infra-red spectroscopy indicate the resulting powder are composed of spinel NiFe2O4 nanoparticle with metal oxygen vibration, crystal properties and lattice strain, all dependent on annealing temperature. Electrochemical charge storage performance of the electrode fabricated from the synthesized material were investigated with the aid of cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy measurements. The obtained results showed that the charge storage performance and rate capability of NiFe2O4 electrode is dependent on the annealing temperature. The study also showed that the electrode from the material annealed at 400 °C demonstrated optimum electrochemical charge storage performance having exhibited optimum specific capacitance and capacity values of 1128 Fg−1 and 58 mAh g−1 at 5 mVs−1 scan rate and 0.5 Ag−1 current density, respectively. The electrode EIS fitted equivalent circuit values were also found dependent on annealing temperature indicating the charge transfer process and rate capability of spinel NiFe2O4 nano-powder can be tailored by simply varying the annealing temperature. The study demonstrates cheap route by which spinel NiFe2O4 powder can be prepared. It also unveils the effect annealing temperature on the microstructural build-up and electrochemical charge storage performance of the material.

Electrochemical Investigation of ZnS/NiO Nanocomposite based Symmetric Supercapattery

AbstractSupercapattery is an ideal energy storage device combining the features of supercapacitors and batteries, offers a high‐energy density as well as high‐power density with extended operational lifespan. In this work, zinc sulfide (ZnS) and zinc sulfide/nickel oxide (ZnS/NiO) nanocomposite was synthesized via chemical coprecipitation method and characterized using state‐of‐the‐art analytical tools. The ZnS/NiO electrode exhibited remarkable electrochemical performance as an electrode material than pure ZnS. The ZnS/NiO nanocomposite exhibited high crystallinity, and spherical nanoparticles with an average grain size of 20–40 nm having a homogeneous dispersion. The ZnS/NiO electrode exhibited an ultrahigh specific capacity of 1803.87 Cg−1 at a relatively low scan rate of 10 mVs−1 in a 1 M KOH solution from cyclic voltammetry and 393 Cg−1 at 16 Ag−1 from charge discharge measurements, and it showed exceptional cycling stability (98 % capacity retention after 1000 cycles). Furthermore, the ZnS/NiO symmetric supercapattery device exhibited 44.43 Fg−1 specific capacitance, 5.52 Wh kg−1 energy density, and 1600 Wkg−1 power density at current density of 0.8 Ag−1 in 1 M KOH solution from galvanostatic charge discharge. After 3000 cycles, the ZnS/NiO nanomaterial demonstrated promising cyclic stability of 95 %. The ZnS/NiO supercapattery nanocomposite might be considered as a potential hybrid electrode material for the future development of electrochemical energy storage devices.

Purification of Spherical Graphite as Anode for Li-Ion Battery: A Comparative Study on the Purifying Approaches.

Graphite is a versatile material used in various fields, particularly in the power source manufacturing industry. Nowadays, graphite holds a unique position in materials for anode electrodes in lithium-ion batteries. With a carbon content of over 99% being a requirement for graphite to serve as an electrode material, the graphite refinement process plays a pivotal role in the research and development of anode materials for lithium-ion batteries. This study used three different processes to purify spherical graphite through wet chemical methods. The spherical graphite after the purification processes was analysed for carbon content by using energy-dispersive X-ray (EDX) spectroscopy and was evaluated for structural and morphological characteristics through X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analyses. The analyses results indicate that the three-step process via H2SO4-NaOH-HCl cleaning can elevate the carbon content from 90% to above 99.9% while still maintaining the graphite structure and spherical morphology, thus enhancing the surface area of the material for anode application. Furthermore, the spherical graphite was studied for electrochemical properties when used as an anode for Li-ion batteries using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements. The results demonstrated that the purification process significantly improves the material's capacity with a specific capacity of 350 mAh/g compared to the 280 mAh/g capacity of the anode made of spherical graphite without purification.

In-situ growth transformation and oxygen vacancy synergistic modulation of the electronic structure of NiCo-LDH enables high-performance hybrid supercapacitors

This article successfully constructs NiCo-LDH nano cages formed by in-situ triggering (IS-LDH), and synergistically modulates the electronic structure by introducing oxygen vacancies. The in-situ triggered generation of NiCo-LDH (IS-LDH) by synthesizing ZIF-67 owns a typical rhombic dodecahedral structure and sensitivity to acid etching. Characterization analysis revealed that the IS-LDH nanocage succeeded the polyhedral structure morphology of ZIF-67 but with multiple vertically aligned nanosheets on the shell. Oxygen vacancies (Ov) were introduced into the IS-LDH through a chemical reduction process using sodium borohydride. The findings demonstrate that the synthesized OvIS-LDH nanocapacitor has a low charge transfer resistance (Rct) with a specific capacitance as high as 1111C g−1 (at 1 A g−1). After 10,000 cycles of charge-discharge measurements, the capacity retention rate was 89.45%. Density functional theory (DFT) calculations confirmed that the inclusion of Ov enhanced the repulsion of OH− by the LDH nanosheets and improved the intrinsic conductivity of LDH. The assembled hybrid supercapacitor (OvIS-LDH//AC) successfully powered an LED light for 20 min. This study proposes a logical approach for developing anode materials that can enhance the performance of supercapacitors.

Synergistic effect of interlayered doping and surface modification to improve the performance of Li-rich manganese-based cathode materials

Li-rich manganese-based oxides (LRMOs) with high energy density have been intensively studied, but their practical use as cathode materials for lithium-ion batteries is still impeded by the shortcomings such as low initial coulombic efficiency, voltage decay and poor rate capability. To address these issues, element Nb is selected to bulk dope and simultaneously surface modify the hierarchical Li1.20Mn0.54Co0.13Ni0.13O2 spheres in this work. Synergistic effect of Nb doping and surface modification on the crystalline structure and electrochemical performance of the resultant LRMOs is characterized in detail. The results suggest that Nb5+ ions are doped into the interlayer sites within the crystals while the LiMn2O4 and LiNb3O8 double layers are coated on the primary nanoparticles. The galvanostatic charge-discharge measurements reveal that the optimal LRMO-Nb2 sample can deliver the capacities of 286 and 167 mAh g−1 at the rates of 0.1 C and 5 C, respectively, and retains a capacity of 191 mAh g−1 at 1 C rate after 200 cycles. Ex-situ XRD patterns prove that the layered structure is strongly pillared by the interlayer-doped Nb5+ during the delithiation/lithiation processes. Especially, some lithium vacancies formed around Nb5+ ions can accelerate the diffusion of Li+ ions, which was proved by DFT calculations and experimental results. Our research demonstrates that cooperating of the interlayered doping of Nb5+ with surface coating of LiNb3O8 layer can improve rate capability and cyclability of the resultant LRMOs significantly.

Activated carbon synthesized from Jack wood biochar for high performing biomass derived composite double layer supercapacitors

In this study, the electrochemical properties of bioderived activated carbon-based electrodes for supercapacitors formed using a sintered ceramic binder were investigated. Activated carbon derived from Jack wood tree (Artocarpus heterophyllus) with variable amounts of TiO2 nanoparticles as a binder, were used as electrodes in order to get good, activated carbon films on FTO substrates. No other binders were used in this study since most conventional binders devastate the electrical conductivity in the films. Furthermore, TiO2 has higher temperature tolerance compared to polymeric binders thus the electrode prepared can be used in wider applications. A series of electrochemical double-layer capacitors were fabricated and characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The supercapacitors prepared showed double-layer capacitive behavior. The electrodes that contain 90 % activated carbon and 10 % TiO2 show optimum performance along with an impressive specific capacitance of 147 F g−1 at 2 mV s−1 scan rate. This supercapacitor exhibits a power density of 68.5 W kg−1 while the energy density is 8.02 Wh kg−1. When the power density is as high as 1186.51 W kg−1 the energy density drops to 5.71 Wh kg−1. According to cyclic voltammetry measurements taken for 1000 cycles, the supercapacitor shows excellent cycle stability without any traces of capacitance drop.

Electrochemical Behavior of Natural Manganese Oxides: Transforming Mining Waste into Energy Storage Materials

The present research explores the potential of manganese oxide waste ore in energy storage applications, focusing on supercapacitors. The investigation assesses the electrochemical capabilities of natural manganese oxides obtained from the Drama region, which has been the main mining center of Greece for manganese ore, especially that of battery-grade quality. Samples were collected from abandoned mining sites in the Kato Nevrokopi area, Drama. The structure and composition of the manganese minerals were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Electrochemical tests involved the preparation of electrodes using natural nsutite and heat-treated nsutite (hausmannite). Then, the designed electrodes were subjected to cyclic voltammetry tests and charge–discharge measurements. The hausmannite electrode exhibited a higher specific capacitance of 667 F/g at a current density of 0.2 A/g, and the electrode material retained 98.3% of its initial capacitance after 1000 cycles. This study provides new perspectives on simple and efficient methods for transforming natural nsutite material from mining waste to hausmannite with greater structural homogeneity and better electrochemical behavior.

Multiwalled-Carbon-Nanotube-Modified Li2ZnTi3O8 as Anode with Improved Cycling Stability and Rate Capability for Lithium-Ion Batteries

Due to its better electronic conductivity and larger lithium intercalation capacity, a multiwalled-carbon-nanotube (MWCNT)-modified Li2ZnTi3O8 (LZTO) has significant potential for use as an anode material for Li-ion batteries. The rapid and affordable ball-mill-aided solid state approach is used to synthesize LZTO with MWCNT-modified Li2ZnTi3O8 (LZTO@MWCNTs). Electrochemical performance tests of the anode material were carried out using cyclic voltammetry (CV), galvanostatic charge-discharge measurement, and electrochemical impedance spectroscopy (EIS). The CV experiments reveal that the LZTO@MWCNT electrode has a lower anodic and cathodic peak potential difference (0.184 V) than the LZTO electrode (0.211 V) and LZTO@MWCNT electrode has better electrochemical reversibility than that of pristine electrode after five cycles utilizing the same procedure. LZTO@ MWCNTs anode material has a higher charge-discharge capacity than LZTO anode material at 0.1–5 C rates. After 100 cycles, the initial discharge capacities of LZTO@MWCNT electrode are 227 and 142 mAh g−1 at the 1C–5C rate, respectively, whereas the initial discharge capacities of LZTO electrode are only144 and 28 mAh g−1 in the same condition. The charge transfer and SEI resistance of the LZTO anode are 19.31 and 62.74 ohms, respectively, after 30 cycles at 1C, according to the EIS data. Additionally, the values for the LZTO@MWCNTs anode are 7.93 and 12.06 ohms for charge transfer and SEI resistance, respectively.

Sr and Fe substituted LaCoO3 nano perovskites: Electrochemical energy storage and sensing applications

Perovskite-type LaCoO3 (LCO), La0.8Sr0.2CoO3 (LSCO), and La0.8Sr0.2Co0.9Fe0.1O3 (LSCFO) were prepared though a sol gel assisted hydrothermal method for supercapacitors and electrochemical sensors for heavy metal ions detection applications. Rhombohedral crystal structure was confirmed using experimental and DFT based computational XRD pattern. LCO, LSCO and LSCFO based modified carbon paste electrodes were prepared for cyclic voltammetry, electrochemical impedance spectra and galvanostatic charge discharge measurements. Among all electrodes, LSCFO results with 715.5 Fg−1 specific capacitance with 97 % retention after 1500 cycles. Cyclic voltammetry measurements for the sensing and detection of heavy metal ions (chromium and mercury) were carried out using all three electrodes and observed that LSCFO showed better response comparatively to that of other two electrodes, thus can be claimed as a potential mixed metal oxide nanomaterial for the fabrication of electrodes for storage of energy and sensor applications.

Graphene aerogel based positive electrode for lithium ion batteries

In this study, a composite of LiNi0.8Mn0.1Co0.1O2 nanoparticles (nNMC-811) supported by three-dimensional (3D) graphene aerogel (GA) was prepared to increase the practical energy density and performance capability of high nickel cathodes. The porous LiNi0.8Mn0.1Co0.1O2 nanoparticle/graphene aerogel (nNMC-811/GA) composite is composed of nNMC-811 and graphene that act as a bridge for electron transfer and acceleration of lithium ion diffusion. nNMC-811 and nNMC-811/GA cathodes characterization data with techniques including X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS) are discussed. Both Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) made clear observations of the uniform distribution of the cathode active powders over the 3D graphene aerogel structure. The electrochemical performance of the nNMC-811 and nNMC-811/GA cathodes was evaluated by the galvanostatic charge-discharge measurement between 2.5 V and 4.5 V at room temperature using a computer-controlled battery tester. In addition, variable speed capacity ratios (C-rate), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analyzes were also performed. nNMC-811/GA hybrid composite structure delivers a specific capacity of 183.15 mAhg−1 at C/2 after the 500th cycle. It is understood from the FE-SEM images taken after the cycle that there is no deterioration in the structure. According to results, it was observed that the 3D porous structure of the nNMC-811/GA composite facilitated the mobility of Li+ ions, and the excellent electrochemical performances of the cathodes were improved due to the increasing defects as well as the electrical conductivity of GA.