Light Enables the Cathodic Interface Reaction Reversibility in Solid-State Lithium-Oxygen Batteries.

Limited triple-phase boundaries arising from the accumulation of solid discharge product(s) in solid-state cathodes (SSCs) pose a challenge to high-property solid-state lithium-oxygen batteries (SSLOBs). Light-assisted SSLOBs have been gradually explored as an ingenious system; however, the fundamental mechanisms of the SSCs interface behavior remain unclear. Here, we discovered that light assistance can enhance the fast inner-sphere charge transfer in SSCs and regulate the discharge products with spherical particles generated via the surface growth model. Moreover, the high photoelectron excitation and transportation capabilities of SSCs can retard cathodic catalytic decay by avoiding structural degradation of the cathode with a reduced charge voltage. The light-induced SSLOBs exhibited excellent stability (170 cycles) with a low discharge-charge polarization overpotential (0.27 V). Furthermore, transparent SSLOBs with exceptional flexibility, mechanical stability, and multiform shapes were fabricated for theory-to-practical applications in sunlight-induced batteries. Our study opens new opportunities for the introduction of solar energy into energy storage systems.

Transforming the Electrochemical Behaviors of Cobalt Oxide from "Supercapacitator" to "Battery" by Atomic-Level Structure Engineering for Inspiring the Advance of Co-Based Batteries.

Cobalt-based electrodes receive emerging attention for their high theoretical capacity and rich valence variation ability, but state-of-the-art cobalt-based electrodes present performance far below the theoretical value. Herein, the in-depth reaction mechanisms in the alkaline electrolyte are challenged and proven to be prone to the surface-redox pseudocapacitor behavior due to the low adsorption energy to OH. Using the atomic-level structure engineering strategy after substitution metal searching, the adsorption energy is effectively enhanced, and the peak of CoOOH can be observed from in situ characterization for the first time, leading to the successful transition of charge storage behavior from "supercapacitor" to "battery". When used in a Zn-Co battery as a proof of concept, it shows comprehensive electrochemical performance with a flat discharge voltage plateau of ≈1.7 V, an optimal energy density of 506 Wh kg-1 , and a capacity retention ratio of 85.1% after 2000 cycles, shining among the reported batteries. As a practical demonstration, this battery also shows excellent self-discharge performance with the capacity retention of 90% after a 10 h delay. This work subtly tunes the intrinsic electrochemical properties of the cobalt-based material through atomic-level structure engineering, opening a new opportunity for the advance of energy storage systems.

Octacalcium Phosphate-Laden Hydrogels on 3D-Printed Titanium Biomaterials Improve Corrosion Resistance in Simulated Biological Media.

The inflammatory-associated corrosion of metallic dental and orthopedic implants causes significant complications, which may result in the implant's failure. The corrosion resistance can be improved with coatings and surface treatments, but at the same time, it might affect the ability of metallic implants to undergo proper osteointegration. In this work, alginate hydrogels with and without octacalcium phosphate (OCP) were made on 3D-printed (patterned) titanium alloys (Ti Group 2 and Ti-Al-V Group 23) to enhance their anticorrosion properties in simulated normal, inflammatory, and severe inflammatory conditions in vitro. Alginate (Alg) and OCP-laden alginate (Alg/OCP) hydrogels were manufactured on the surface of 3D-printed Ti substrates and were characterized with wettability analysis, XRD, and FTIR. The electrochemical characterization of the samples was carried out with open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was observed that the hydrophilicity of Alg/OCP coatings was higher than that of pure Alg and that OCP phase crystallinity was increased when samples were subjected to simulated biological media. The corrosion resistance of uncoated and coated samples was lower in inflammatory and severe inflammatory environments vs. normal media, but the hydrogel coatings on 3D-printed Ti layers moved the corrosion potential towards more nobler values, reducing the corrosion current density in all simulated solutions. These measurements revealed that OCP particles in the Alg hydrogel matrix noticeably increased the electrical charge transfer resistance at the substrate and coating interface more than with Alg hydrogel alone.

Direct Electrochemistry of Glucose Dehydrogenase-Functionalized Polymers on a Modified Glassy Carbon Electrode and Its Molecular Recognition of Glucose.

A glucose biosensor was layer-by-layer assembled on a modified glassy carbon electrode (GCE) from a nanocomposite of NAD(P)+-dependent glucose dehydrogenase, aminated polyethylene glycol (mPEG), carboxylic acid-functionalized multi-wall carbon nanotubes (fMWCNTs), and ionic liquid (IL) composite functional polymers. The electrochemical electrode was denoted as NF/IL/GDH/mPEG-fMWCNTs/GCE. The composite polymer membranes were characterized by cyclic voltammetry, ultraviolet-visible spectrophotometry, electrochemical impedance spectroscopy, scanning electron microscopy, and transmission electron microscopy. The cyclic voltammogram of the modified electrode had a pair of well-defined quasi-reversible redox peaks with a formal potential of -61 mV (vs. Ag/AgCl) at a scan rate of 0.05 V s-1. The heterogeneous electron transfer constant (ks) of GDH on the composite functional polymer-modified GCE was 6.5 s-1. The biosensor could sensitively recognize and detect glucose linearly from 0.8 to 100 µM with a detection limit down to 0.46 µM (S/N = 3) and a sensitivity of 29.1 nA µM-1. The apparent Michaelis-Menten constant (Kmapp) of the modified electrode was 0.21 mM. The constructed electrochemical sensor was compared with the high-performance liquid chromatography method for the determination of glucose in commercially available glucose injections. The results demonstrated that the sensor was highly accurate and could be used for the rapid and quantitative determination of glucose concentration.

Thermally Driven Structural Order of Oligo(Ethylene Glycol)-Terminated Alkanethiol Monolayers on Au(111) Prepared by Vapor Deposition.

To probe the effects of deposition temperature on the formation and structural order of self-assembled monolayers (SAMs) on Au(111) prepared by vapor deposition of 2-(2-methoxyethoxy)ethanethiol (CH3O(CH2)2O(CH2)2SH, EG2) for 24 h, we examined the surface structure and electrochemical behavior of the resulting EG2 SAMs using scanning tunneling microscopy (STM) and cyclic voltammetry (CV). STM observations clearly revealed that EG2 SAMs vapor-deposited on Au(111) at 298 K were composed of a disordered phase on the entire Au surface, whereas those formed at 323 K showed improved structural order, showing a mixed phase of ordered and disordered phases. Moreover, at 348 K, uniform and highly ordered EG2 SAMs on Au(111) were formed with a (2 × 3√3) packing structure. CV measurements showed sharp reductive desorption (RD) peaks at -0.818, -0.861, and -0.880 V for EG2 SAM-modified Au electrodes formed at 298, 323, and 348 K, respectively. More negative potential shifts of RD peaks with increasing deposition temperature are attributed to an increase in van der Waals interactions between EG2 molecular backbones resulting from the improved structural quality of EG2 SAMs. Our results obtained herein provide new insights into the formation and thermally driven structural order of oligo(ethylene glycol)-terminated SAMs vapor-deposited on Au(111).

New Insight into the Mechanism of Multivalent Ion Hybrid Supercapacitor: From the Effect of Potential Window Viewpoint.

Multivalent ion hybrid supercapacitors have been developed as the novel electrochemical energy storage systems due to their combined merits of high energy density and high power density. Nevertheless, there are still some challenges due to the limited understanding of the electrochemical behaviors of multivalent ions in the electrode materials, which greatly hinders the large scale applications of its based hybrid supercapacitors. Herein, the long-term electrochemical behaviors of MnO2 -based electrode in the divalent Mg2+ ions electrolyte are systematically studied and linked with the morphological and electronic evolution of MnO2 by cycling at different potential windows (spanning to 1.2 V). It reveals that the different potential windows result in the different electrochemical behaviors, which can be divided into two ranges (below and above -0.2 V). And, the electrode cycled at a potential window of 0-1.2 V delivers the highest capacitance of 967 F g-1 at a scan rate of 10 mV s-1 , in which the MnO2 is transformed into a uniformly distributed and nonagglomerated nanoflake morphology promoting the intercalation and deintercalation of Mg2+ ions. This study will enrich the understanding of the charge storage mechanism of multivalent ions and provide significant guidance on the performance improvement of the hybrid supercapacitors.

Optimized terbium doped Ti/PbO2 dimensional stable anode as a strong tool for electrocatalytic degradation of imidacloprid waste water.

The presence of pesticides in water has emerged as a momentous environmental issue over the past decades. Herein, a terbium doped Ti/PbO2 (denoted as Ti/PbO2-Tb) dimensionally stable Ti/PbO2-Tb anode has been successfully prepared by one-step electrodeposition path for electrocatalytic degradation of imidacloprid (IMD) wastewater with high efficiency. Ti/PbO2-Tb electrode presents higher oxygen evolution potential, lower charge transfer resistance, stronger stability, longer service lifetime and outstanding electrocatalytic activity than Ti/PbO2 electrode. The optimum condition for IMD oxidation is obtained by analyzing the effects of some critical operating parameters including temperature, initial pH, current density and electrolyte concentration. It is proved that 70.05% of chemical oxygen demand and 76.07% of IMD are removed after 2.5 h of degradation under current density of 8 mA cm-2, pH 9, temperature 30 °C and 7.0 g L-1 NaCl electrolyte. In addition, the electrode displays commendable energy saving property as well as favorable reusability. The degradation mechanism of IMD is proposed by analyzing the intermediates identified by LC-MS. The present research provides a feasible strategy to degrade IMD wastewater by Ti/PbO2-Tb electrode.

Antioxidant and electrochemical properties of cultivated Pleurotus spp. and their sporeless/low sporing mutants.

Methanolic extracts of four cultivated edible mushrooms of Pleurotus spp. namely Pleurotus florida, Pleurotus sajor-caju, Pleurotus cystidiosus and Pleurotus djamor along with the sporeless/low sporing mutants of Pleurotus florida, and Pleurotus sajor-caju were analyzed for their antioxidant activity using different chemical assays. The electrochemical behaviors of these extracts were also analyzed using cyclic voltammetry and differential pulse voltammetry. Results showed that scavenging effects on 2,2-diphenyl-1-picrylhydrazyl radicals were good (73.3-42.4 %) at 1.5 mg/ml. At 12 mg/ml, the reducing powers (2.54-1.71) and chelating effects on ferrous ions (56.0-78.5 %) were excellent. H2O2 scavenging abilities at 1.5 mg/ml showed a wide range (20.0-85.4 %). Scavenging of superoxide radicals were excellent and were found to be in the range of 61.1-90.0 % at 16 mg/ml concentration. FRAP results were in the range of 1.20 - 0.98 at 16 mg/ml. Total phenolic and total flavonoid contents of the methanolic extracts ranged from 22.67 to 36.03 mg/g and 1.19-2.94 µg/g respectively. The study assessed the amount of variation in antioxidant activities exhibited by different cultivated species and their sporeless/low sporing mutants.

In Vitro Characterization of Hydroxyapatite-Based Coatings Doped with Mg or Zn Electrochemically Deposited on Nanostructured Titanium.

Biomaterials are an important and integrated part of modern medicine, and their development and improvement are essential. The fundamental requirement of a biomaterial is found to be in its interaction with the surrounding environment, with which it must coexist. The aim of this study was to assess the biological characteristics of hydroxyapatite (HAp)-based coatings doped with Mg and Zn ions obtained by the pulsed galvanostatic electrochemical method on the surface of pure titanium (cp-Ti) functionalized with titanium dioxide nanotubes (NTs TiO2) obtained by anodic oxidation. The obtained results highlighted that the addition of Zn or Mg into the HAp structure enhances the in vitro response of the cp-Ti surface functionalized with NT TiO2. The contact angle and surface free energy showed that all the developed surfaces have a hydrophilic character in comparison with the cp-Ti surface. The HAp-based coatings doped with Zn registered superior values than the ones with Mg, in terms of biomineralization, electrochemical behavior, and cell interaction. Overall, it can be said that the addition of Mg or Zn can enhance the in vitro behavior of the HAp-based coatings in accordance with clinical requirements. Antibacterial tests showed that the proposed HAp-Mg coatings had no efficiency against Escherichia coli, while the HAp-Zn coatings registered the highest antibacterial efficiency.

Well designed iridium-phosphinite complexes: Biological assays, electrochemical behavior and density functional theory calculations.

Mononuclear phosphinite Iridium complexes based on ferrocene group have been prepared and characterized by various spectroscopic techniques. The complexes were subjected to cyclic voltammetry studies in order to determine the energies of HOMO and LUMO levels and to estimate their electrochemical and some electronic properties. Organic complex-based memory substrates were immobilized using TiO2-modified ITO electrodes, and the memory functions of phosphinite-based organic complexes were verified by chronoamperometry (CA) and open-circuit potential amperometry (OCPA). Extensive theoretical and experimental investigations were directed to gain a more profound understanding of the chemical descriptors and the diverse electronic transitions taking place within the iridium complexes, as well as their electrochemical characteristics. The quantum chemical calculations were carried out for the iridium complexes at the DFT/CAM-B3LYP level of theory in the gas phase. Furthermore, the antioxidant, antimicrobial, DNA binding, and DNA cleavage activities of the complexes were tested. Complex 2 exhibited the highest radical scavenging activity (67.5 ± 2.24 %) at 200.0 mg/L concentration. It was observed that the complexes formed an inhibition zone in the range of 8-15 mm against Gram + bacteria and in the range of 0-13 mm against Gram - bacteria. The agarose gel electrophoresis method was used to determine the DNA binding and DNA cleavage activities of the complexes. All of the tested complexes had DNA binding activity; however, complexes 1, 2, and 8 showed better binding activity than the others.

Advancing Dental Implant Design: A Comprehensive Study of Machining Parameters, Corrosion Behavior, and Microstructural Evaluation.

In this research, we investigate the impact of varying machining parameters [depth of cutting (mm) and spindle rotation speed (rpm)] on the microstructure and electrochemical behavior of Ti6Al4V-ELI dental implants. This comprehensive study employs an approach, leveraging potentiodynamic methods and electrochemical impedance spectroscopy, to analyze corrosion behavior in a phosphate-buffered saline solution. To further deepen our understanding of corrosion kinetics, we used an alternating current circuit model, based on a simple Randles equivalent circuit. This model elucidates the corrosion interface interactions of the Ti6Al4-V-ELI alloy implant within the PBS solution. In addition, our research delves into the microstructural implications of different machining parameters, utilizing scanning electron microscopy and X-ray diffraction (XRD) techniques to reveal significant phase changes. The changes in texture were examined qualitatively by comparing the intensities of the peaks of the XRD pattern. A detailed correlation analysis further links the machining parameters with the corrosion properties of dental implants, offering a comprehensive perspective rarely explored in the existing literature. The results obtained for the three samples showed that the corrosion resistance would be higher by increasing the machining depth and the spindle rotation and that the corrosion current would be lower. As a result, a lower corrosion rate was obtained. Finally, experimental results from electrochemical analyses are compared and discussed.

Discharge Properties and Electrochemical Behaviors of Mg-Zn-xSr Magnesium Anodes for Mg-Air Batteries.

In this work, the electrochemical and discharge properties of Mg-Zn-xSr (x = 0, 0.2, 0.5, 1, 2, and 4 wt.%) alloys used as anodes for Mg-air batteries were systematically studied via microstructure characterization, electrochemical techniques, and Mg-air battery test methods. The addition of Sr refines the grain size, changes the composition and morphology of the passivation film and discharge products, and enhances the electrochemical properties of the alloy. Excessive Sr addition breaks the grain boundaries and precipitates a large number of Sr-rich phases, resulting in microgalvanic corrosion and the 'chunk effect'. The anode efficiency of Mg-Zn-1Sr is the highest at a current density of 10 mA cm-2, reaching 61.86%, and the energy density is 2019 mW h g-1. Therefore, Sr is a microalloying element that can optimize the electrochemical performance of Mg-air battery alloy anodes.

Insight into the Storage Mechanism of Sandwich-Like Molybdenum Disulphide/Carbon Nanofibers Composite in Aluminum-Ion Batteries.

Aluminum-ion batteries (AIBs) have become a research hotspot in the field of energy storage due to their high energy density, safety, environmental friendliness, and low cost. However, the actual capacity of AIBs is much lower than the theoretical specific capacity, and their cycling stability is poor. The exploration of energy storage mechanisms may help in the design of stable electrode materials, thereby contributing to improving performance. In this work, molybdenum disulfide (MoS2) was selected as the host material for AIBs, and carbon nanofibers (CNFs) were used as the substrate to prepare a molybdenum disulfide/carbon nanofibers (MoS2/CNFs) electrode, exhibiting a residual reversible capacity of 53 mAh g-1 at 100 mA g-1 after 260 cycles. The energy storage mechanism was understood through a combination of electrochemical characterization and first-principles calculations. The purpose of this study is to investigate the diffusion behavior of ions in different channels in the host material and its potential energy storage mechanism. The computational analysis and experimental results indicate that the electrochemical behavior of the battery is determined by the ion transport mechanism between MoS2 layers. The insertion of ions leads to lattice distortion in the host material, significantly impacting its initial stability. CNFs, serving as a support material, not only reduce the agglomeration of MoS2 grown on its surface, but also effectively alleviate the volume expansion caused by the host material during charging and discharging cycles.

Cavitation erosion-corrosion properties of as-cast TC4 and LPBF TC4 in 0.6 mol/L NaCl solution: A comparison investigation.

In this work study, a comparative analysis was undertaken to investigate investigation into the cavitation erosion (CE) and corrosion behavior of laser powder bed fusion (LPBF) TC4 and as-cast TC4 in 0.6 mol/L NaCl solution. Relevant results indicated that LPBF TC4 revealed a rectangular checkerboard-like pattern with a more refined grain size compared to as-cast TC4. Meanwhile, LPBF TC4 surpassed its as-cast counterpart in CE resistance, demonstrating approximately 2.25 times lower cumulative mass loss after 8 h CE. The corrosion potential under alternating CE and quiescence conditions demonstrated that both LPBF TC4 and as-cast TC4 underwent a rapid potential decrease at the initial stages of CE, while a consistent negative shift in corrosion potential was observed with the continuously increasing CE time, indicative of a gradual decline in repassivation ability. The initial surge in corrosion potential during the early CE stages was primarily attributed to accelerated oxygen transfer. As CE progressed, the significant reduction in corrosion potential for both LPBF TC4 and as-cast TC4 was attributed to the breakdown of the passive film. The refined and uniform microstructure in LPBF TC4 effectively suppresses both crack formation and propagation, underscoring the potential of LPBF technology in enhancing the CE resistance of titanium alloys. This work can provide important insights into developing high-quality, reliable, and sustainable CE-resistant materials via LPBF technology.

Electrochemical behavior and surface stability of dental zirconia ceramics in acidic environments.

Dental zirconia ceramics, widely employed in dentistry for their biocompatibility and mechanical properties, face challenges in long-term viability within the oral cavity. This study focuses on analyzing the electrochemical behavior of a commercial dental zirconia ceramic type in acidic environments. Through extensive electrochemical investigations, including Electrochemical Impedance Spectroscopy (EIS) and cyclic polarization resistance (Cpol), corrosion resistance was assessed. Despite indications of material dissolution, our results demonstrate significant corrosion resistance, as reflected in low corrosion current density (Icorr) values. Notably, the study reveals the development of a protective oxide layer at the ceramic-electrolyte interface, contributing to material stability. XRD analysis confirms the presence of stable crystallographic phases (t-ZrO2) even after exposure to acidic media. Surface characterizations utilizing scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX) affirm minimal surface damage and maintained elemental composition. These findings illuminate the intricate electrochemical behavior of dental zirconia ceramics in challenging environments, underscoring their potential for durable dental restorations. This interdisciplinary research bridges dentistry and materials science, providing valuable insights for optimizing material properties and advancing dental materials and restorative techniques.

Study of Precipitated Secondary Phase at 700 °C on the Electrochemical Properties of Super Duplex Stainless Steel AISI2507: Advanced High-Temperature Safety of a Lithium-Ion Battery Case.

Super duplex stainless steel (SDSS) is a suitable structural material for various engineering applications due to its outstanding strength and corrosion resistance. In particular, its high-temperature strength can enhance the safety of electronic products and cars. SDSS AISI2507, known for its excellent strength and high corrosion resistance, was analyzed for its microstructure and electrochemical behavior at the ignition temperature of Li-ion batteries, 700 °C. At 700 °C, AISI2507 exhibited secondary phase precipitation values of 1% and 8% after 5 and 10 h, respectively. Secondary phase precipitation was initiated by the expansion of austenite, forming sigma, chi, and CrN phases. The electrochemical behavior varied with the fraction of secondary phases. Secondary phase precipitation reduced the potential (From -0.25 V to -0.31 V) and increased the current density (From 8 × 10-6 A/cm2 to 3 × 10-6 A/cm2) owing to galvanic corrosion by sigma and chi. As the fraction of secondary phases increased (From 0.0% to 8.1%), the open circuit potential decreased (From -0.25 V to -0.32 V). Secondary phase precipitation is a crucial factor in reducing the corrosion resistance of SDSS AISI2507 and occurs after 1 h of exposure at 700 °C.

The rapid synthesis of 1,10-phenanthroline-5,6-diimine (Phendiimine) and its fascinating photo-stimulated behavior.

Here, for the first time, we report synthesis of 1,10-phenanthroline-5,6-diimine (Phendiimine) based on an acid catalysed SN2 reaction of 1,10-phenanthroline-5,6-dione and 2-picolylamine in EtOH as a solvent. The synthesized Phendiimine molecule showed excellent photo-sensitivity against visible light, together with photoluminescence in both water and ethanol and also, it showed electrochemical activity with Fe electrode in ethanol and H2SO4 solution. Tauc plot also showed Phendiimine is a direct band-gap semiconductor. The hot-point probe test also showed that it is a n-type semiconductor. The UV-vis. absorption maximum shift in two solvents (water and ethanol) demonstrates the solvatochromism behavior of the molecule. The practical significance of this work and its guiding implication for future related research can be outlined as follows. Based on the results obtained, it appears that the Phendiimine molecule could revolutionize the medical field, potentially in the design of artificial eyes, increasing the yield of photovoltaic cells through enhanced heat transfer, improving computers and industrial photo-cooling systems, serving as photo-controller in place of piezoelectric devices, functioning as electronic opt couplers, controlling remote lasers, changing convection in photothermal heaters, designing miniaturized real photo-stimulated motors, creating photo or thermal switches through spin crossover complexes, developing electronic light-dependent resistance (LDR) devices, constructing X-ray and gamma-ray detectors, designing intelligent clothing, creating photo dynamic tumour therapy (PDT) complexes, singlet fission materials in solar cells and more.

Corrosion Resistance of Al0.5CoCrFeNiCuxAgy (x = 0.25, 0.5; y = 0, 0.1) High-Entropy Alloys in 0.5M H2SO4 Solution.

The electrochemical behavior of the as-cast Al0.5CoCrFeNiCuxAgy (x = 0.25, 0.5; y = 0, 0.1) high-entropy alloys (HEAs) in a 0.5M H2SO4 solution was studied. Polarization measurements were carried out in a standard three-electrode electrochemical cell at room temperature using a platinum counter electrode and a saturated silver chloride reference electrode. For Al0.5CoCrFeNiCu0.5 and Al0.5CoCrFeNiCu0.5Ag0.1, copper segregation along the grain boundaries was observed, which highly dissolved in the sulfuric acid solution and resulted in low corrosion resistance of the samples. Introducing Ag into Al0.5CoCrFeNiCu0.25 HEA led to the precipitation of a copper-silver eutectic structure, in which the copper regions were selectively dissolved in the sulfuric acid solution. Al0.5CoCrFeNiCu0.25 exhibited the best corrosion resistance with the corrosion current density of Icorr = 3.52 ± 0.02 µA/cm2, significantly superior to that of the Al0.5CoCrFeNi sample without copper and silver (Icorr = 6.05 ± 0.05 µA/cm2). Finally, the results indicated that suppressing elemental segregation by annealing or tailoring chemical composition is essential to improve the corrosion resistance of Al0.5CoCrFeNiCuxAgy HEAs.

RGO nanosheet wrapped ß-phase NiCu2S nanorods for advanced supercapacitor applications.

A new integration strategy of transition metal sulfide with carbon-based materials is used to boost its catalytic property and electrochemical performances in supercapacitor application. Herein, crystalline reduced graphene oxide (rGO) wrapped ternary metal sulfide nanorod composites with different rGO ratios are synthesized using hydrothermal technique and are compared for their physical, chemical, and electrochemical performances. It is found that their properties are tuned by the weight ratios of rGO. The electrochemical investigations reveal that ß-NiCu2S/rGO nanocomposite electrode with 0.15 wt.% of rGO is found to possess maximum specific capacitance of 1583 F g-1 at current density of 15 mA g-1 in aqueous electrolyte medium. The same electrode shows excellent cycling stability with capacitance retention of 89% after 5000 charging/discharging cycles. The reproducibility test performed on NiCu2S/rGO nanocomposite electrode with 0.15 wt.% of rGO indicates that it has high reproducible capacitive response and rate capability. Thus, the present work demonstrates that the ß-NiCu2S/rGO nanocomposite can serve as a potential electrode material for developing supercapacitor energy storage system.

Facile and Scalable Development of High-Performance Carbon-Free Tin-Based Anodes for Sodium-Ion Batteries.

Tin (Sn)-based anodes for sodium (Na)-ion batteries possess higher Na-storage capacity and better safety aspects compared to hard carbon -based anodes but suffer from poor cyclic stability due to volume expansion/contraction and concomitant loss in mechanical integrity during sodiation/desodiation. To address this, the usage of nanoscaled electrode-active particles and nanoscaled-carbon-based buffers has been explored, but with compromises with the tap density, accrued irreversible surface reactions, overall capacity (for "inactive" carbon), and adoption of non-scalable/complex preparation routes. Against this backdrop, anode-active "layered" bismuth (Bi) has been incorporated with Sn via a facile-cum-scalable mechanical-milling approach, leading to individual electrode-active particles being composed of well-dispersed Sn and Bi phases. The optimized carbon-free Sn-Bi compositions, benefiting from the combined effects of "buffering" action and faster Na transport of Bi, to go with the greater Na-storage capacity and lower operating potential of Sn, exhibit excellent cyclic stability (viz., ∼83-92% capacity retention after 200 cycles at 1C) and rate capability (viz., no capacity drop from C/5 to 2C, with only ∼25% drop at 5C), despite having fairly coarse particles (∼5-10 µm). As proven by operando synchrotron X-ray diffraction and stress measurements, the sequential sodiation/desodiation of the components and, concomitantly, stress build-ups at different potentials provide "buffering" action even for such "active-active" Sn-Bi compositions. Furthermore, the overall stress development upon sodiation of Bi has been found to be significantly lower than that of Sn (by a factor of ∼3.8), which renders Bi promising as a "buffer" material, in general. Dissemination of such complex interplay between electrode-active components during electrochemical cycling also paves the way for the development of high-performance, safe, and scalable "alloying-reaction"-based anode materials for Na-ion batteries and beyond, sans the need for ultrafine/nanoscaled electrode particles or "inactive" nanoscaled-carbon-based "buffer" materials.