Galvanostatic Charge Discharge Tests Research Articles

Development of single-atom Ru and N, S-Co-doped carbon catalyst for enhanced cycling stability of lithium-oxygen batteries

Li-oxygen (Li-O2) battery is a novel energy storage equipment. However, its poor reaction reversibility relating to the insoluble lithium peroxide (Li2O2) generated during the discharge process, limits its application and development for large scale use. Therefore, the design and synthesis of effective catalysts which can efficiently catalyze the production and decomposition of Li2O2 and exclude the generation of side-products has become the primary task to develop Li-O2 batteries. Herein, a new type of electrocatalyst based on single-atom Ru and N, S-co-doped carbon materials (Ru/CNS/CNT) is introduced to reduce the overpotential of the battery reaction and accelerate the formation and decomposition of Li2O2. Galvanostatic charge-discharge tests were performed on the Li-oxygen (Li-O2) battery with Ru/CNS/CNT as the cathode catalyst material. With a limited specific capacity of 1000 mA h g−1, the battery can stably cycle for 79 cycles at a current density of 200 mA g−1. Furthermore, the existence of the single atom of Ru was demonstrated according to the characterization of HAADF-STEM. The experimental results showed that composite material Ru/CNS/CNT can accelerate the formation and decomposition of lithium peroxide (Li2O2), thereby greatly improving the cycling stability of the battery.

Superior compatibility of silicon nanowire anodes in ionic liquid electrolytes

Silicon nanowire anodes were investigated in lithium-metal cells using different electrolyte formulations based on 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide and N -trimethyl-N -butyl-ammonium bis(fluoro sulfonyl)imide ionic liquids. The lithium insertion process in the silicon anode was analyzed by cyclic voltammetry measurements, performed at different scan rates and for prolonged cycles, combined with impedance spectroscopy analysis. A galvanostatic charge-discharge cycling test was performed to analyze the electrochemical performances using different types of ionic liquids. A study of the Solid Electrolyte Interphase layer on the silicon nanowire electrode surface was carried out through X-ray photoelectron spectroscopy. In general, the silicon anodes in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide-based electrolytes show very good reversibility, reproducibility, and efficiency in the lithiation process, even at high scan rates, and exhibit a reversible capacity exceeding 1,000 mA h g-1 after 2,000 charge-discharge cycles, corresponding to 46% of the initial value.

Facile Synthesis of Ag-Doped Urchin-like MnO2 on Carbon Cloth for Supercapacitors.

Based on MnO2/carbon cloth (CC) composite materials, an Ag-doped MnO2 nanowire, self-assembled, urchin-like structure was synthesized in situ on the surface of CC using a simple method, and a novel and efficient flexible electrode material for supercapacitors was developed. The morphology, structure, elemental distribution, and pore distribution of the material were analyzed using SEM, TEM, XRD, XPS, and BET. The electrochemical performance was tested using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). In the three-electrode system, GCD testing showed that the specific capacitance of the material reached 520.8 F/g at 0.5 A/g. After 2000 cycles at a current density of 1 A/g, the capacitance retention rate was 90.6%, demonstrating its enormous potential in the application of supercapacitor electrode materials.

Investigation of the performance and properties of ZnO/GO double-layer supercapacitor

Composite electrode material was formed by mixing reduced graphene oxide (rGO) and zinc oxide (ZnO) compound, using the Hummers and green synthesis methods, respectively. Of rGO powder, 10 g was mixed with 10%, 20% and 30% ZnO, and composite electrodes were obtained by using 10% binder. The energy storage performance and structural characteristics of the supercapacitor were evaluated by analyzing the capacitance values of the synthesized electrodes. The structural characterization of ZnO/rGO composites was performed using X-ray diffraction and field-emission scanning electron microscopy. The electrochemical properties of the ZnO/GO electrodes were analyzed by cyclic voltammetry, electrochemical impedance and galvanostatic charge–discharge tests. The specific capacitance value of electrodes increased as zinc content increased in the ZnO/rGO composite material used to produce electrodes. The maximum specific capacitance values were measured at 5 mV/s scanning rate as 194.23 (rGO), 366.81 (10% ZnO), 383.18 (20% ZnO) and 410.48 F/g (30% ZnO). In conclusion, the use of composite material formed by the combination of ZnO nanoparticles obtained by green synthesis method from orange peel and graphene oxide increased the electrochemical efficiency of the supercapacitor.

Tip and heterogeneous effects co-contribute to a boosted performance and stability in zinc air battery

The zinc-air battery (ZAB) performance and stability strongly depend on the structure of bifunctional electrocatalyst for oxygen reduction/evolution reaction (ORR/OER). In this work, we combine the tip and heterogeneous effects to construct cobalt/cobalt oxide heterostructure nanoarrays (Co/CoO-NAs). Due to the formed heterostructure, more oxygen vacancies are found for Co/CoO-NAs resulting in a 1.4-fold higher ORR intrinsic activity than commercial carbon supported platinum electrocatalyst (Pt/C) at 0.8 V versus reversible hydrogen electrode (vs. RHE). Moreover, a fast surface reconstruction is observed for Co/CoO-NAs during OER catalysis evidenced by in-situ electrochemical impedance spectroscopy and Raman tests. In addition, the tip effect efficiently lowers the mass transfer resistance triggering a low overpotential of 347 mV at 200 mA cm−2 for Co/CoO-NAs. The strong electronic interplay between cobalt (Co) and cobalt oxide (CoO) contributes to a stable battery performance during 1200 h galvanostatic charge–discharge test at 5 mA cm−2. This work offers a new avenue to construct high-performance and stable oxygen electrocatalyst for rechargeable ZAB.

Development of a new electrodeposited AgSbS2/FTO electrode: Comparison of supercapacitance in Li-based aqueous and organic electrolytes

AgSbS2, or "miargyrite" material, could be a viable option for high-storage-capacity electrodes, guaranteeing exceptional performance. This document describes the production of AgSbS2/FTO thin films by the co-electrodeposition technique on Fluorine-doped-Tin-Oxide (FTO). To optimize the amount of silver, the films were deposited at a single potential −1.28/SCE, by varying [Ag+] between 0.01 and 0.03 M in aqueous conditions. Structurally, XRD-RAMAN analyses confirmed the formation of AgSbS2 thin films with cubic poly-crystallization. After elaboration, the thin films were analyzed morphologically, optically and electrochemically to better define their physico-chemical performances. This study proved through comparison that the co-electrodeposited AgSbS2/FTO electrode behaves as a pseudo-capacitor in aqueous and organic media based on LiOH (1 M) dissolved in water and acetonitrile within potential windows of [-0.9, 0 V] and [-0.8, 0.4 V]/SCE respectively. More precisely, using cyclical voltammetry (CV) analysis, the comparison revealed that the AgSbS2/FTO electrode presented a maximum specific capacity of about 1278 F/g in LiOH-water and 706 F/g in LiOH-acetonitrile. Finally, during the galvanostatic charge-discharge test, an 18 % and 4 % decrease in specific rate capacity was estimated as current density increased in LiOH-water and LiOH-acetonitrile respectively.

New Liquid Electrolytes Consisting of Li Salts and Urea Derivatives for Li-Ion Batteries

Deep eutectic solvents are mixtures that exhibit melting points much lower than those of the endmembers due to the molecular interactions. Deep eutectic solvents attracted attention because high melting point compounds are available as flame-resistance solvents.1 However, the stable operation of Li-ion batteries (LIBs) with deep eutectic electrolytes (DEEs) is still challenging probably due to their high protonic nature and consequent narrow potential window.2 To develop Li-ion DEEs with a wide potential window, we investigated DEEs based on lithium bis(fluorosulfonyl)amide (LiFSA) and a series of urea derivatives to clarify the correlation between compound structure and electrolyte properties. Furthermore, we examined the electrode performances of the Li4Ti5O12 (LTO) negative electrode and LiNi1/3Co1/3Mn1/3O2 (NCM) positive electrode in the DEEs.To prepare DEEs, urea derivatives, such as urea, 1-methylurea, 1,3-dimethylurea, 1,1-dimethylurea, and tetramethyl urea are mixed with LiFSA at molar ratios of 1:2 or 1:4 at room temperature. The oxidation and reduction stability was evaluated by linear sweep voltammetry (LSV) in three-electrode cells with Pt foil as the working electrode. Galvanostatic charge-discharge tests were performed in three-electrode cells with LTO or NCM working electrodes and activated carbon counter electrodes.The prepared LiFSA:urea derivative (1:4) mixtures (LiFSA:urea, LiFSA:1,3-dimethylurea, and LiFSA:tetramethylurea) became transparent liquids at room temperature. Moreover, LiFSA:1,3-dimethylurea and LiFSA:tetramethylurea were clear liquid at even in 1:2 mixtures. Using the five DEEs, we evaluated their electrolyte properties. Figure 1 shows the LSV curves of the DEEs. Among the five deep eutectic liquids, LiFSA:1,3-dimethylurea (1:2) exhibited the widest potential window of 4.49 V, showing an even wider potential window than electrolytes with non-protonic tetramethyl urea.Figure 2a displays the charge-discharge curves of LTO electrodes in the DEEs. The LiFSA:urea (1:4) electrolyte cell exhibits a large irreversible capacity, and its initial reversible capacity is 228 mAh g-1, significantly larger than the theoretical capacity. This indicates that side reactions possibly takes place in addition to the LTO charge-discharge reaction. On the other hand, the LiFSA:1,3-dimethylurea (1:2) electrolyte demonstrates stable and reversible charge-discharge for 50 cycles, with an initial discharge capacity of 179 mAh g-1, which is close to the theoretical capacity. The LiFSA:tetramethylurea cell showed lower cycle stability than the LiFSA:1,3-dimethylurea cell, possibly due to electrolyte precipitation during cycling because LiFSA:tetramethylurea (1:2) electrolyte is an almost saturated solution.Using the LiFSA:1,3-dimethylurea (1:2) DEE, we further evaluated the electrochemical performance of the NCM electrode as shown in Figure 2b. The NCM electrode showed reversible charge-discharge behavior over 10 cycles with moderate capacity of 75.7 mAh g-1. These results demonstrate the potential applicability of the DEE to 3 V-class LIBs. In the presentation, we will also discuss the optimization of LiFSA concentration to improve battery properties and the observation of the formation of surface films on the electrodes in DEEs.

K x Mn[Mn(CN)6] as a High Capacity Positive Electrode Material for Potassium Batteries

Recently, Na-ion and K-ion batteries have attracted attention as next-generation secondary batteries.1 Prussian blue analogues (PBAs) are promising cathode materials for these batteries. In 2014, it was reported that Na x Mn[Mn(CN)6] exhibited higher capacity in Na cells than the theoretical capacity based on Mn2+/3+ redox, which could be attributed to the reduction of Mn in [Mn(CN)6] to monovalence.2 Thus, PBA with Mn at the C-coordination site exhibits unique properties, but there is no report of high capacity in K cells. In this study, K x Mn[Mn(CN)6] (KMnHCM) was synthesized, and K+ ion extraction/insertion properties were evaluated. KMnHCM was synthesized by the solution precipitation method.3 The solution was sufficiently deoxygenated by bubbling nitrogen gas, and synthesis was performed under N2 atmosphere. The obtained samples were washed three times with deionized water under N2 atmosphere, and then dried at 150 °C under vacuum. The active material was mixed with conductive carbon (KB) and binder (PVdF) at a weight ratio of 7:2:1 in a glove box under an Ar atmosphere. Galvanostatic charge-discharge tests were conducted in a two-compartment three-electrode cell using a composite electrode coated on an Al foil as the working electrode, an activated carbon counter electrode, and an Ag+/Ag reference electrode. Figure 1(a) shows the X-ray diffraction (SXRD) patterns and Rietveld refinement results of the synthesized sample. The diffraction patterns of KMnHCM can be attributed to the monoclinic structure with space group P21/n and are almost identical to that previously reported. SXRD patterns were successfully fitted with the satisfied R values, and the composition of KMnHCM was estimated to be K1.87Mn[Mn(CN)6]0.96·0.29H2O. Figure 1(b) shows the charge-discharge curves of KMnHCM. The electrode showed an initial charge capacity of 163 mAh g-1 and an initial discharge capacity of 220 mAh g-1, corresponding to respective ~2.0 and 2.76 potassium extraction and insertion, respectively, from/into K x Mn[Mn(CN)6]. The discharge capacity exceeds the theoretical capacity of 160 mAh g-1 based on the Mn2+/3+ redox of K1.87Mn[Mn(CN)6]0.96·0.29H2O. Furthermore, the additional plateau was observed at the low voltage of around 1.5 and 1.7 V in the discharge and charge curves, respectively. The extremely high capacity and the third plateau at low voltage are similar to Na x Mn[Mn(CN)6] in Na cells.2 Thus, the third plateau would be attributed to the reversible redox of [MnII(CN)6]4-⇄[MnI(CN)6]5-. In the talk, we will further discuss the charge-discharge mechanisms, including redox behavior and structural changes of KMnHCM during charge/discharge.

On Synthesis and Electrochemical Performance of Na4Fe3(PO4)2(P2O7) Cathode for Sodium-Ion Batteries

Developing cost-effective and large-scale energy storage systems (ESSs) has been an important topic over the past years in order to implement efficient utilization of renewable electricity generated from sources like solar, wind, geothermal and tidal energy (1). Since the commercialization in 1991, lithium-ion batteries (LIBs) have been widely used in portable electronics, electric vehicles (EVs), and energy storage devices (2). However, there is an increase in demand for alternative energy sources based on abundant and low-cost materials due to the limited reserves and high costs of lithium compounds. In this context, sodium-ion batteries (SIBs) have received great attention because of their similarities to LIBs and the large abundance (2.3%) on earth, and low cost of sodium compounds (3). However, the energy density of most SIBs are lower that of LIBs, primarily due to the larger ionic radius and higher mass of Na+ ion compared to Li+ ions, as well as the lower electrochemical potential of sodium cells relative to lithium cells (4). Many efforts have been devoted to the development of high-performance cathode materials, including layered transition metal oxides, Prussian blue analogues (PBAs), sulfates, phosphates and pyrophosphates. Polyanionic compounds, in particular, are considered as promising cathode materials with regard to their high working voltage, structural stability, thermal stability and small volume change upon cycling (5). For example, iron phosphate-based materials have gained attention inspired by LiFePO4 for LIBs. However, the olivine NaFePO4 is predominantly produced through an ion exchange process (6). The maricite NaFePO4 is electrochemically inactive due to the lack of Na migration channels within its structure. On the other hand, Na2FeP2O7 shows long cycle life and structural stability with a low capacity because of its single electron diffusion process. Na4Fe3(PO4)2(P2O7) (NFPP) combines the benefits of both phosphate and pyrophosphate, offering potential advantages such as low-cost, environmental friendliness, high average working voltage (~ 3.1 V vs. Na+/Na), favorable theoretical capacity (129 mAh g-1), low volume change (< 4%) due to its open framework composed of [Fe3P2O13] layers connected by (P2O7)4- groups with 3D ion channels and low activation barriers for Na+ transport as well as structural and thermal stability. However, NFPP is susceptible to the formation of impurities such as NaFePO4 and Na2FeP2O7, which can arise from the synthesis temperature and adopted reaction materials, potentially restricting the electrochemical performance of NFPP. Additionally, the inherent insulating characteristics of the (PO4)3- group in NFPP may result in reduced electronic conductivity and slow ion diffusion, which hinders its practical application (7, 8). Therefore, various strategies have been developed to enhance conductivity such as nanosizing, carbon coating and metal ion doping.NFPP can be synthesized by various methods like solid-state, sol-gel, spray drying and combustion. In this study, we present our results on employing both sol–gel and combustion methods with distinct synthesis parameters. The structure, morphology and particle size of NFPP are characterized by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) techniques. The electrochemical performance of NFPP cathodes is investigated in both half- and full-cells via galvanostatic charge-discharge cycling tests. Keywords: sodium-ion batteries, cathode material, iron-based mixed phosphate, sol-gel synthesis, large scale M. Armand and J. M. Tarascon, Nature, 451, 652 (2008).J. B. Goodenough and K.-S. Park, Journal of the American Chemical Society, 135, 1167 (2013).B. Dunn, H. Kamath and J.-M. Tarascon, Science, 334, 928 (2011).M. H. Han, E. Gonzalo, G. Singh and T. Rojo, Energy & Environmental Science, 8, 81 (2015).P. Barpanda, L. Lander, S.-i. Nishimura and A. Yamada, Advanced Energy Materials, 8, 1703055 (2018).K. T. Lee, T. N. Ramesh, F. Nan, G. Botton and L. F. Nazar, Chemistry of Materials, 23, 3593 (2011).X. Wu, G. Zhong and Y. Yang, Journal of Power Sources, 327, 666 (2016).H. Kim, I. Park, S. Lee, H. Kim, K.-Y. Park, Y.-U. Park, H. Kim, J. Kim, H.-D. Lim, W.-S. Yoon and K. Kang, Chemistry of Materials, 25, 3614 (2013).

Performance optimization of the symmetric supercapacitors based on paddy straw-derived porous activated carbon

The utilization of porous carbon material derived from sustainable, cost-effective, and renewable biomass for supercapacitor electrode applications has garnered significant attention in recent times. In this work, activated carbon was synthesized via the carbonization of paddy straw, succeeded by activation using different molarity levels (3 M to 6 M) of the activating agent. X-ray diffraction, fourier-transform infrared spectroscopy, N2 physisorption, and field-emission scanning electron microscopy were employed to characterize various parameters of the synthesized activated carbon derived from paddy straw (ACP). The process of activation considerably increased the specific surface area up to 1358.087 m2 g−1 establishing a well-developed intercalated tunnelled porous surface morphology that promotes charge accumulation. The electrochemical characteristics of the activated carbon were evaluated in a 6 M KOH electrolyte using techniques such as cyclic voltammetry, galvanostatic charge-discharge tests, and impedance spectroscopy. The highest specific capacitance of 396 F g−1 at the current density of 1 A g−1 was obtained for the single electrode of ACP-5 M. At a current density of 1 A g−1 the symmetric ACP-5 M based symmetric device provided a specific energy of 38.8 Wh k g−1 at a specific power of 604 W k−1. The paddy straw-derived activated carbon demonstrates versatile potential as an electrode material for energy storage applications due to its impressive electrochemical properties, well-developed porosity, and remarkable capacitance retentions of 90.6 % in 6 M KOH following 10,000 charge-discharge cycles.

Understanding the benefits of Al3+-doping on NaSICONs explained through an out-of-the-scheme isovalent substitution of Fe3+ in Na3Fe2(PO4)3 series

NaSICON fast-ionic conductors have been largely considered as a viable solution for the development of energy storage units. Chemical doping is a popular technique to improve their electrochemical performance, and the widely accepted criterion is an aliovalent substitution, to increase the cationic density, and/or an isovalent substitution with larger species, to enlarge the bottleneck, as widely speculated for the LATP series. However, this study demonstrates through electrochemical impedance spectroscopy that the ionic conductivity of a Na3Fe2(PO4)3 NaSICON isovalently doped with smaller Al3+ ions to form a Na3AlxFe2-x(PO4)3 NaSICON series can be improved up to 4 times. We resorted to X-ray diffraction and ab initio simulation to show that the NaSICON bottlenecks are enlarged despite the lattice shrinkage and the long-range diffusion path is unlocked for x ≥ 0.5. Moreover, the Al-doping sizeably increases the cohesive energy of the monoclinic lattice, thus stabilizing it. As a result, the cyclic voltammetry and galvanostatic charge-discharge tests of the half-cell battery with Na3AlxFe2-x(PO4)3 as the composite cathode showed better capacity and no decay. We believe that this out-of-the-scheme work will clarify the effects of Al-doping on NaSICON compounds and at the same time contribute to reviving the interest around this highly-sustainable Fe3+-based NaSICON.

Functionalized, bio-derived carbon-aerogel/Li4Ti5O12 composites as anode materials for Li-ion batteries

In this work we investigate the electrochemical behavior of bio-derived carbon-aerogel/Li4Ti5O12 composites (CAG/LTO) in Li-ion half cells. The studied CAG/LTO samples were successfully prepared through the gelatinization process of potato starch precursor with pristine LTO material, followed by controlled pyrolysis in an inert gas atmosphere. The obtained composites were examined by elemental analysis (EA), X-ray diffraction (XRD), N2-adsorption/desorption (N2-sorption), scanning and transmission electron microscopy (SEM, TEM), galvanostatic charge/discharge tests (GCDT), extensive cycling (LT-GCDT) and cyclic voltammetry (CV) methods. The results show, that carbon aerogel compressive matrix significantly improved the electrical conductivity of LTO anode material and was effective only in its composite form. The best electrochemical parameters and overall performance was achieved by 16% CAG/LTO composite. After extensive cycling (1016 charge/discharge cycles under 5 C), its discharge capacity was equal to 209 mAh/g, achieving the capacity retention of 106%.

High-performance Ti-doped V2O5 coating on the Ni-rich layered cathode: Construction and theoretical calculation

Surface coating had been widely acknowledged as an effective method to improve the electrochemical performance of the cathodes for lithium-ion batteries (LiBs). In this study, a high-conductivity Ti0.05V1.96O5 (TVO) coating was successfully deposited on the surface of Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) particles. The crystal structure, micro morphology and element composition of the resulted NCM811 @TVO samples were evaluated using X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. Subsequently, the electrochemical performance of NCM811 @TVO cathodes were evaluated by galvanostatic charge/discharge tests (GCDT) and electrochemical impedance spectroscopy (EIS). The experimental results suggested that incorporating a TVO coating on the NCM811 cathode effectively enhanced both the rate capability and the cycling stability. Furthermore, first-principles calculation based on the density functional theory (DFT) were performed to elucidate the distinct electronic structure and Li ion migration behavior of V2O5 and TVO. The DFT calculation demonstrated that the introduction of Ti ions into the V2O5 leaded to the formation of small polarons and excessive free electrons, while significantly reduced the energy barrier for Li+ migration along [100] direction.

Chrysanthemum flower-like copper molybdenum oxide decorated graphene oxide nanoribbon composite: A novel positive electrode material for asymmetric supercapacitor devices

This study used hydrothermal followed by ultrasonic methods to generate a composite of CuMoO4-adorned graphene oxide nanoribbons that resembled Chrysanthemum flowers (CuMoO4/GONR). The as-prepared materials were confirmed using a variety of physicochemical methods. Different electrochemical approaches were used to determine the supercapacitor efficiency of at-the-time-fabricated electrodes, including cyclic voltammetry (CV), Galvanostatic charge-discharge tests (GCD), and electrochemical impedance spectroscopy (EIS). The findings demonstrate that compared to pure CuMoO4 and GONR matrixes, CuMoO4/GONR composite deserves dominance, such as more surface area, the occurrence of multiple active sites, improved penetration/diffusion ability, and excellent conductivity. The CuMoO4/GONR composite demonstrated a significant capacitance retention of 89 % at 5 A/g and delivered a comparably high specific capacitance of 865 F/g at 1 A/g. The prepared CuMoO4/GONR//AC asymmetric device showed a 41.7 Wh/kg energy density at 1058 W/kg power density. The obtained results validated CuMoO4/GONR composite as the promising source of electrode material used in supercapacitor devices.

Preparation and electrochemical performance of NiCo2S4 nanoelectrode materials

In this paper, NiCo2S4 nanoelectrode materials were prepared by a two-step hydrothermal method. Physical and morphological characterization and electrochemical testing revealed that the prepared NiCo2S4 has a sea urchin-like layered three-dimensional network structure, which can fully increase the contact area with the electrolyte, increase the active sites and improve the electrochemical performance. The specific capacitance of the prepared NiCo2S4 nanomaterials reached 717.32 F/g. The cyclic voltammetry test curve as well as galvanostatic charge-discharge (GCD) test curve have perfect symmetry, good material reversibility. Electrochemical impedance spectroscopy (EIS) indicates materials with low impedance. The specific capacitance remained 76.8% after 3000 cycles and the electrochemical stability was good. NiCo2S4 electrode material has excellent electrochemical properties and has a promising application in supercapacitor electrodes.

One-step electrochemical synthesis of FTO/MnO2-graphene composite for electrochemical energy storage

The FTO/MnO2-Graphene composite was prepared using a one-step electrochemical approach employing chronoamperometry. Graphene was synthesized via electrochemical exfoliation and characterized using Raman spectroscopy and transmission electron microscopy (TEM).The prepared composite film exhibiting an extraordinary structure offers a large surface area provided with several channels to enhance the rapid diffusion of ions and electron transport owing to the grapheme sheets content. Various characteristics of the composite films have been investigated through X ray diffraction (XRD). Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and UV–Vis spectroscopy. To evaluate the electrochemical performance of the FTO/MnO2 and FTO/MnO2-GR films, cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge tests were conducted. The specific capacitance was found at 5 mV·s−1, to be 192.3 F g−1 with graphene and 73.5 F g−1 without. This increase in capacitance upon incorporating grapheme sheets suggests that FTO/MnO2-GR composite film would have many potential applications as suitable materials for supercapacitor electrodes and energy storage devices. The FTO/MnO2-GR in a asymmetric supercapacitor demonstrated an excellent reversible operation, delivering an energy density of 3 W h kg−1 at a specific power of 25 W/ kg. Furthermore, even after 1000 cycles, the FTO/MnO2-GR asymmetric supercapacitor retains an impressive 99 % of its capacitance.

Investigation of supercapacitor electrode performances of phosphorus-doped graphene oxide electrodes in various deep eutectic solvents and symmetric supercapacitor application

A one-step preparation method of phosphorus-doped graphene oxide electrode (P-GOE) was used as electrode material for high-performance supercapacitors. Phosphorus-doped graphene oxides were synthesized on pencil graphite electrodes in one step with easy, cheap, and non-toxic chemicals by using the chronoamperometric process. Electrochemical analyses were carried out to examine the capacitive behavior of the electrodes in different deep eutectic solvents (DESs) (choline chloride:ethylene glycol (ChCl:EG), choline chloride:urea (ChCl:U), choline chloride:phenol (ChCl:Ph)). The electrolytes used make research valuable because these electrolytes were environmentally friendly, non-toxic, and inexpensive. Electrodes were analyzed by cyclic voltammetry at different scan rates, charge-discharge test at different current densities, 1000-cycle galvanostatic charge-discharge test, and electrochemical impedance spectroscopy (EIS). Structural and morphological properties of the electrodes were investigated by FTIR, XRD, SEM, BET, and XPS. As a result of the characterization and electrochemical analysis, it was seen that the phosphorus doping to the electrodes were carried out successfully. The maximum areal capacitances of phosphorus-doped graphene oxide electrodes were calculated to be 450 mF.cm−2, 140 mF.cm−2, and 400 mF.cm−2 in electrolytes for supercapacitor applications. In this study, high-performance P-doped graphene oxide electrodes were produced with an easy method using inexpensive and non-toxic solvents, providing an important contribution as environmentally friendly and sustainable electrode materials for supercapacitor applications.

Unveiling the electrochemical advantages of a scalable and novel aniline-derived polybenzoxazole-reduced graphene oxide composite decorated with manganese oxide nanoparticles for supercapacitor applications

In the quest for better supercapacitor performance, materials with high energy storage, rapid charge transfer and excellent charge-discharge capabilities are crucial. However, improving energy density and optimizing electrode materials for supercapacitors remains a challenge. Within this perspective, we developed a novel aniline-derived polybenzoxazole-reduced graphene oxide composite (Mn3O4-pBOA-rGO) for supercapacitor applications. An electrode for supercapacitor applications was then fabricated using the synthesized composite. Various characterization techniques, such as X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, were employed to analyze the structure of the material and cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests were performed to evaluate the supercapacitive performance. Remarkably, the Mn3O4-pBOA-rGO ternary nanocomposite-based electrode exhibited enhanced electrochemical performance achieving an energy density of 116 Wh kg−1 in a 1 M aqueous Na2SO4 electrolyte at a current density of 1 A g−1. In comparison, the Mn3O4-pBOA binary nanocomposite recorded an energy density of 25 Wh kg−1, while bare Mn3O4 yielded 10 Wh kg−1. The significantly improved electrochemical properties of the Mn3O4-pBOA-rGO composite present a promising and viable solution for supercapacitor applications.

High performance polythiophene derivative with good electrochromic and energy storage properties electrochemical synthesized in boron trifluoride diethyl etherate

In this study, novel poly(3,4-dibromothiophene) (PDBrTh) is firstly prepared through electrochemical polymerization method using boron trifluoride diethyl etherate (BF3·Et2O) as polymeric solvent. In BF3·Et2O, the electrochemical oxidation potential of 3,4-dibromothiophene is significantly reduced compared with in Acetonitrile/Tetrabutylammonium tetrafluoroborate (ACN/TBATFB) system, which provides conditions for high quality polymer preparation. The prepared PDBrTh in BF3·Et2O shows good electrochemical activity and thermal stability. The electrochromic and supercapacitive performance of the prepared PDBrTh are also studied. The color of the prepared PDBrTh can be reversibly changed between red and blue with fast response time and high optical contrast. Galvanostatic charge-discharge test shows that the prepared PDBrTh also has good electrochemical energy storage performance. The specific capacitance value of the PDBrTh can reach to 229.6 F g−1 under the current density of 1 A g−1, showing good energy storage capacity. An all-polythiophenes electrochromic supercapacitor device (ESD) is constructed by prepared PDBrTh and poly(3,4-ethylenedioxythiophene), the color of the device can change between red and dark blue. The ESD also shows good energy storage property and robust charge-discharge stability. Moreover, the ESD shows obvious color changes and corresponding light transmittance changes during the charging and discharging process, realizing intelligent visual monitoring of the energy storage state. This study shows that the prepared PDBrTh has good practical application potential in the field of intelligent wearable energy storage.

Morphology induced symmetrical supercapacitive performance of the 3D interconnected Ni(OH)2 framework

The rational design of electrode materials for energy storage applications is a key element of resolving the energy crisis. Herein, nickel hydroxide (NHO) nanostructures with different morphologies, such as platelet (Platelets-NHO), three-dimensional flower (3DF-NHO), and flake-like (Flakes-NHO) morphologies, were synthesized using different solvents inside the hydrothermal reactor during the reaction process. The fabricated electrode materials of the NHO nanostructure were further characterized using different types of microscopic and spectroscopic techniques, and their electrochemical performance was further studied in a three-electrode assembly cell to explore the morphological effect on the supercapacitive performance. The 3DF-NHO displayed a significantly enhanced capacitance value (1112.5 F g−1) than Platelets-NHO (820.0 F g−1) and Flakes-NHO (850.0 F g−1) at the same current load (1 A g−1). The electrochemical supercapacitive performance of 3DF-NHO, Platelet-NHO, and Flakes-NHO revealed that the morphology played an important role in enhancing the electrode chemical performance of the electrode material. The symmetric assembly cell of 3DF-NHO was also assembled, and cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and cyclic stability tests were recorded, revealing excellent performance for potential applications in the field of energy storage devices. Among the materials, the excellent performance of 3DF-NHO is credited to the three-dimensional structures and interconnected petals, which provide a better surface and suitable space for the electrolytes during the electrochemical reaction. These results suggest that the rational design of the electrode material using an appropriate solvent could help to fabricate a large number of different morphologies of NHO, which may be a potential candidate for energy storage electrode materials.