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The electrochemical response, and hence the performance, of lithium-ion batteries (LIBs) is heavily influenced by the microstructure of their electrode material, particularly grain size. Thus, a model that correlates electrode microstructure with electrochemical response can aid in optimizing these characteristics for better battery performance. However, no existing studies address this modeling problem. This study fills this gap by using data-driven probabilistic modeling to map the electrochemical response (voltammograms) to electrode grain size. The methodology is demonstrated on six datasets containing voltammograms from in-silico cyclic voltammetry experiments on LiMn2O4 electrode particles. Feature vectors created using seven features of the voltammogram were combined with the corresponding known grain size values to construct data-driven probabilistic models via Gaussian process regression (GPR) with five different kernels for each dataset. The hyperparameters of the kernels used in these GPR models were optimized using grid-search. Performance evaluation through bias-variance analysis demonstrated strong predictive accuracy of the developed models. Additionally, the comparisons across datasets and kernels showed the Gaussian and Rational Quadratic kernels' effectiveness in modeling various relationships. The obtained results substantiate the efficacy of the proposed approach, revealing significant insights and encouraging further exploration. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation of cyclohexane to KA oil, a mixture of cyclohexanone and cyclohexanol, holds great promise for decarbonized chemical manufacturing based on the value of products and the thermodynamic equilibrium potential. However, fundamental understanding of this reaction is extremely limited. For example, even the number of electrons in this reaction has not yet been identified. In this work, we elucidate the mechanism of electrochemical cyclohexane oxidation to KA oil on fluorine-doped tin oxide (FTO), platinum, and glassy carbon anodes. Using three-electrode electroanalysis, isotopic labeling, and concentration studies, we show that electrochemical cyclohexane oxidation to KA oil is similar to its thermochemical analogue in that O2, not water, is the primary oxygen source. The reaction is initiated through the formation of cyclohexyl or hydroxyl radicals, depending on electrode and electrolyte composition. Additionally, crossover from undivided two-electrode cells is found to impact measurements such that cathodic reaction and reactor design may introduce potential artifacts to anodic activity and selectivity. These findings have significant implications for the technological viability of a theoretically promising electrosynthesis process. [ABSTRACT FROM AUTHOR]

Structural and electrochemical properties of bismuth ferrite nanostructures produced by pulsed laser deposition with various morphologies are reported. The nanostructures are also explored as electrode materials for high-performance supercapacitors. Scanning electron microscopy images revealed that various bismuth ferrite morphologies were produced by varying the background pressure (10−6, 0.01, 0.10, 0.25, 0.50, 1.0, 2.0 and 4.0 Torr) in the deposition chamber and submitting them to a thermal treatment after deposition at 500 ◦C. The as-deposited bismuth ferrite nanostructures range from very compact thin-film (10−6, 0.01, 0.10 Torr), to clustered nanoparticles (0.25, 0.50, 1.0 Torr), to very dispersed arrangement of nanoparticles (2.0 and 4.0 Torr). The electrochemical characteristic of the electrodes was investigated through cyclic voltammetry process. The increase in the specific surface area of the nanostructures as background pressure in the chamber increases does not lead to an increase in interfacial capacitance. This is likely due to the wakening of electrical contact between nanoparticles with increasing porosity of the nanostructures. The thermal treatment increased the contact between nanoparticles, which caused an increase in the interfacial capacitance of the nanostructure deposited under high background pressure in the chamber. [ABSTRACT FROM AUTHOR]

The development of bioelectrochemical systems requires careful selection of both their biotic and abiotic components to obtain sustainable devices. Herein, we report a biophotoelectrode obtained with polyhydroxybutyrate (PHB), a biopolymer, which purple non-sulphur bacteria produce as an energy stock under specific environmental conditions. The electrode was obtained by casting a mixture composed of PHB and carbon fibers in a 3:2 mass ratio. Following, the composite material was modified with polydopamine and thermally treated to obtain a hydrophilic electrode with improved electrochemical behavior. The bio-based electrode was tested with metabolically active cells of Rhodobacter capsulatus embedded in a biohybrid matrix of polydopamine. The system achieved enhanced catalytic activity under illumination, with an 18-fold increase in photocurrent production compared to biophotoelectrodes based on glassy carbon, reaching a current density of 12 ± 3 μ A cm−2, after 30 min of light exposure at +0.32 V. The presented biocompatible electrode provides a sustainable alternative to metal-based and critical raw material-based electrodes for bioelectrochemical systems. [ABSTRACT FROM AUTHOR]

While lithium-ion batteries (LIBs) are approaching their energy limits, lithium metal batteries (LMBs) are undergoing intensive investigation for higher energy density. Coupling LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode with lithium (Li) metal anode, the resultant Li||NMC811 LMBs are among the most promising technologies for future transportation electrification, which have the potential to realize an energy density two times higher than that of state-of-the-art LIBs. To maximize their energy density, the Li||NMC811 LMBs are preferred to have their cathode loading as high as possible while their Li anode as thin as possible. To this end, we investigated the effects of different cathode active material loadings (2–14 mg cm−2) on the performance of the Li||NMC811 LMBs. Our study revealed that the cathode loadings have remarkably affected the cell performance, in terms of capacity retention and sustainable capacity. Cells with high cathode loadings are more liable to fade in capacity, due to more severe formation of the CEI and more sluggish ion transport. In this study, we also verified that the protection of the Li anode is significant for achieving better cell performance. In this regard, our newly developed Li-containing glycerol (LiGL) via molecular layer deposition (MLD) is promising to help boost the cell performance, which was controllably deposited on the Li anode. [ABSTRACT FROM AUTHOR]

The aim of this work is to overcome the problem of agglomeration and volumetric changes observed in reduced graphene oxide (rGO) and polyaniline (PANI) nanocomposites responsible for inferior capacitive performance. The synergistic effect of optimized rGO, PANI and tellurium (Te) ternary nanocomposite was investigated for the electrochemical performances for the energy storage devices. For this purpose, the electrochemical test was performed at low molar 0.1M H2SO4 concentration of aqueous electrolyte in a two-electrode cell assembly. The electrochemical studies showed that the specific capacitance of 564F g−1 is attained in rGO/PANI nanocomposite electrode cell whose capacitive performance showed an increase by adding different concentration of Te. The maximum specific capacitance of 895 F g−1 at 10 mV s−1 was observed in rGO/PANI/Te50 (GPT50) with negligible charge transfer resistance, knee frequency ∼466.63 Hz, low response time ∼17.39 s, high coulombic efficiency ∼92% and high energy and power densities of 41 Wh kg −1 and 3679 W kg −1 with cyclic stability of ∼91% after 5000 GCCD cycles respectively. The electrochemical performances result of the electrode material indicated that the combination of Te with rGO and PANI can be used to enhance the supercapacitor performances of the rGO/PANI nanocomposite electrodes. This novel composition has overall improved the electrochemical studies of the electrode materials and thus can be used as a suitable candidate for supercapacitor devices. [ABSTRACT FROM AUTHOR]

The structural transformations, oxygen releasing and side reactions with electrolytes on the surface are considered as the main causes of the performance degradation of Li-rich layered oxides (LROs) cathodes in Li-ion batteries. Thus, stabilizing the surfaces of LROs is the key to realize their practical application in high energy density Li-ion batteries. Surface coating is regarded as one of the most effective strategies for high voltage cathodes. The ideal coating materials should prevent cathodes from electrolyte corrosion and possess both electronic and Li-ionic conductivities simultaneously. However, commonly reported coating materials are unable to balance these functions well. Herein, a new type of coating material, La2CuO4 was introduced to mitigate the surface issues of LROs for the first time, due to its superb electronic conductivity (26–35 mS⋅cm−1) and lithium-ionic diffusion coefficient (10−12–10−13 cm2⋅s−1). After coating with the La2CuO4, the capacity retention of Li1.2Ni0.54Co0.13Mn0.13O2 cathode was increased to 85.9% (compared to 79.3% of uncoated cathode) after 150 cycles in the voltage range of 2.0–4.8 V. In addition, only negligible degradations on the deliverable capacity and rate capability were observed. [ABSTRACT FROM AUTHOR]

Due to their comparable electrical properties, pencil graphite electrodes (PGE) have become a more popular electrode in electrochemical applications than traditional carbon electrodes, mostly because of their affordability and availability, which allows for disposable applications. Both cyclic voltammetry (CV) and chronoamperometry (CA) techniques were used to develop a new disposable modified pencil graphite electrode based on the electropolymerization of 1,5-diaminonaphthalane (1,5-DAN). Characterization results confirmed that the modified p-1,5-DAN/PGE(CV) sensor showed much enhanced sensitivity and lower resistivity than the bare and p-1,5-DAN/PGE(CA) sensor, therefore, it was used for the sensitive and selective voltammetric determination of flufenamic acid (FFA). Under the optimum experimental conditions, the p-1,5-DAN/PGE(CV) sensor showed limits of detection (LOD) and quantitation (LOQ) of 4.97 × 10-10 (0.14 ng ml-1) and 1.66 × 10-9 M (0.47 ng ml-1), respectively, applying square wave anodic stripping voltammetry method. The p-1,5-DAN/PGE(CV) sensor also exhibits good accuracy, repeatability, storage stability and selectivity for detecting FFA in biological fluids. These results confirms that the developed p-1,5-DAN/PGE(CV) sensor is more sensitive to measuring FFA in biological fluids, pharmaceutical formulations, and pharmacokinetic studies compared with the previous electrochemical sensors. [ABSTRACT FROM AUTHOR]

Lithium supply shortages have prompted the search for alternatives to widespread grid system applications. Potassium-ion batteries (PIBs) have emerged to promising candidates for this purpose. Nonetheless, the large radius of K+ (1.38 Å) impedes the march of satisfactory cathode materials. Here, we used solid-phase synthesis to prepare a layered K0.37MnO2·0.25H2O (KMO) cathode, comprising alternately connected MnO6 octahedra with a large interlayer spacing (0.71 nm) to accommodate the migration and transport of K+ ions. The cathode material achieved initial specific capacities of 102.3 and 88.1 mA h g−1 at current densities of 60 mA g−1 and 1 A g−1, respectively. The storage mechanism of K+ ions in PIBs was demonstrated ex situ using x-ray diffraction, x-ray photoelectron spectroscopy, and Raman spectroscopy measurements. Overall, our proposed KMO was confirmed as an auspicious cathode material for potential use in PIBs. [ABSTRACT FROM AUTHOR]

2D decorated nanostructures are fast emerging as efficient electrode materials for electrochemical devices. Au decorated SnO2, synthesized using co-precipitation and hydrothermal methods, can become a useful electrode material for supercapacitors. Au incorporation helps to mitigate the conductivity issues of SnO2 nanostructures. The superior 2D-flake like morphology leads to appreciable performance enhancement, with specific capacitance of 234 F g−1 at 1 A g−1 current density, which is much larger than that observed in pristine SnO2. The high cycling stability of Au-decorated SnO2 clearly shows its usefulness for high-performance supercapacitors. A theoretical model is also reported to explain the electrochemical results. [ABSTRACT FROM AUTHOR]

Pi-MnO2-rGO-CFP electrode was developed through a concurrent deposition of Pi-MnO2 and reduced graphene oxide (rGO) on carbon fiber paper (CFP). Cyclic voltammetry (CV) and electrochemical impedance studies (EIS) were applied for the electrochemical characterization of the electrode. The electro catalytic activity of the modified electrode was improved by the increased synergistic characteristics of the CFP and electrochemically deposited rGO-Pi-MnO2 composite. The performance of the modified electrode was remarkable due to its lowest charge transfer resistance (Rct), and highest surface area offering more active sites and quicker electron transport kinetics. X-ray diffraction spectroscopy (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and optical profilometry (OP) were employed to study the physicochemical properties. Furthermore, the modified electrode was availed to oxidize piperonyl alcohol mediated by 4- acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl (4-acetamido TEMPO or 4-ACT). The product obtained was purified and characterized by ¹HNMR. The turnover frequency of 4-ACT was studied at different concentrations of the reactant, and the reaction parameters were also optimized using statistical tool design of experiment. This methodology is demonstrated to be economical, environmentally benign, and highly efficient in obtaining piperonal as it is carried out under milder reaction conditions. [ABSTRACT FROM AUTHOR]

Lithium-rich materials exhibit high capacity and high voltage properties due to the charge compensation mechanism, but the disadvantages such as material voltage decay and poor cycling stability limit their practical application. The fixation and stabilizations of surface lattice oxygen is considered the most challenging problem the materials. We have successfully prepared a lithium-rich cathode material with a triad of oxygen vacancies, surface spinel and polyanionic SO42- doping by a mild surface preactivation treatment, and systematically investigated the stabilization mechanism of surface oxygen vacancies in the materials. The VS-LR0.25 material with multiple stabilizations of oxygen vacancies exhibited excellent cycling stability and rate performance, with an initial Coulomb efficiency of 82.7%, and capacity retention of 95.1% after 200 cycles at 1 C. [ABSTRACT FROM AUTHOR]

While substantial electrocatalysts have been proposed and efficiently catalyze CO2 to multiple products, mass transport is becoming a major constraint to further improve the performance of CO2 electrochemical reduction reaction (CO2ERR). Gas diffusion electrode (GDE) technique has been identified as an effective way to overcome the confined mass transfer of CO2. While many research efforts have focused on the catalyst layer (CL), considerably fewer efforts have focused on the gas diffusion layer (GDL), the support and substrate of GDE. Herein, we studied the effect of the GDL on the performance of phthalocyanine cobalt (CoPc)-based GDE to catalyze CO2 to CO with a special emphasis on the hydrophilicity, porosity, and wettability. We demonstrate a facile and reproducible method of PTFE impregnation to tune the hydrophobicity and pore characteristics of GDL, to enhance CO2ERR. Using a proper designed GDL as the substrate, the CoPc-based GDE achieves a high current density of 321.7 mA cm-2 and Faradaic efficiency for CO of 98.4% at a cathode potential of -1.2 V (vs RHE), representing the highest performance of CoPcbased GDEs reported in the literature. [ABSTRACT FROM AUTHOR]

Doping of Ni-rich LNMC cathode materials with tungsten via solid-state route has been shown to stabilize the materials against structural degradation at high voltages during electrochemical cycling. Here we use a wet-chemical doping method to homogeneously introduce 0.5 mol% tungsten into dense NMC811 (Li[(Ni0.8Mn0.1Co0.1)]O2), followed by a detailed structural and electrochemical characterization. A homogeneous distribution of W in the materials was evidenced by elemental mapping and TOF-SIMS. The increase in bond-dissociation energy to oxygen (BDEO) of the transition metal (TM) site led to compressed slab thickness (TMO6 octahedron width in c-direction), indicating shorter, and thus strengthened, TM-O bonds, as also confirmed by TGA-MS results. Importantly, statistical analysis of electron backscatter diffraction (EBSD) data revealed a W-induced radial alignment of a-b planes of the primary particles. The cycling stability of the doped material was more than 7% higher for the Wdoped (92.4%) as compared to the undoped NMC811 (85.3%) material at a higher upper cut-off voltage of 4.5 V vs Li/Li+. Furthermore, the voltage decay was lower (0.2 V vs 0.29 V), leading to >2% lower energy loss (5.3% vs 7.4%) for the W-doped material. [ABSTRACT FROM AUTHOR]

Designing in-plane supercapacitors with high electrode materials selectivity is an indispensable approach to improve electrochemical performance. In this work, a facile template method was employed to fabricate in-plane supercapacitors. This template method could select any electrochemical active materials as electrode materials of in-plane supercapacitors. Hence, a high electrochemical performance material Mnâ€"Co LDO-2S with optimized metal-sulfur bonds proportion and abundant sulfur vacancies was employed as electrode material of symmetrical in-plane supercapacitor (SPS). SPS exhibits excellent electrochemical performance finally, and has considerable area energy density 55.0 ÎĽ Wh cmâˆ'2 with an area power density of 0.7 mW cmâˆ'2. As a result, introducing sulfur atoms and sulfur vacancies are efficient approaches to improve electrode materials’ electrochemical performance, and template method that proposed in this work is a promising approach to widen selectivity of in-plane supercapacitors’ electrode materials. [ABSTRACT FROM AUTHOR]

The electrochemical performance of Li-rich layered manganese oxide (LMO) cathodes is greatly affected by the oxygen release and irreversible transition metal (TM) migration. Such structural instabilities are the driving force behind structural reconstruction, rapid voltage decay, and capacity fade in LMR cathodes. This is due to the inability to retain a layered-layered phase during cycling hence the inability to maintain a consistent conductive ion flow (lithiums). Herein, we report for the first time, exploration of manganese and oxygen-compensated nanostructures to investigate its role in the structural morphology and microstructure. The nanostructures were studied using the molecular dynamics simulation method owing to its ability to simulate nucleation and crystal growth. According to the analysis, the simulated nanospheres yielded multi-grained and single crystalline phases for Mn and O compensation, respectively. Further analysis illustrated severe Li/O loss in the structure when the role of oxygen is neglected. Moreover, the formation of layered-layered-spinel composites is demonstrated together with the comparison of temperaturedependent diffusion coefficients. This goes to show that both oxygen and manganese play a crucial role during the cycling process of Li-rich cathode materials. These findings can provide important insights into understanding diffusion and ageing mechanisms in cathode materials during the cycling processes. [ABSTRACT FROM AUTHOR]

By providing a facile and scalable alternative to otherwise complex and resource-intensive synthesis of graphene, laser-induced graphene (LIG) is spearheading the translation of graphene-based propositions to deployable technologies for societal benefit. LIG is a versatile and economical synthesis approach which is being used on a variety of substrates and in a multitude of applicationsâ€"including miniaturized sensing systems. One aspect that has not been addressed thoroughly in LIG-based miniaturized sensing systems is its successful integration with microfluidics and its possible use in point-of-care settings. To further diversify the applications of LIG with integrated microfluidics, this work reports on the development of an integrated flexible microfluidics-LIG based electrochemical biosensor. The work describes the methodology to develop a polydimethylsiloxane-LIG scribed polyamide microfluidic device in a leakage-free flexible application. In view of the excellent electrical and electrochemical properties of LIG, such device has been employed for electrochemical biosensing. The biosensing capabilities of the microfluidic device were validated via sensing of cardiac troponin Iâ€"a gold standard cardiac biomarker for early identification of acute myocardial infarction (AMI). The developed biosensor demonstrated a detection and quantification limit of 45.33 pg mlâˆ'1 and 151.10 pg mlâˆ'1 respectively, which are in clinically significant ranges for diagnosis of AMI. The µ -fluidic biosensor was also analyzed for stability and interference with other cardiac biomarkers. The developed integrated µ -fluidic electrochemical biosensor was evaluated for possible point-of-source applications in conjunction with a custom 3D printed peristaltic pump and smartphone-enabled miniaturized potentiostat. [ABSTRACT FROM AUTHOR]

The world is in the process of transitioning towards a more sustainable energy future, with green hydrogen considered an attractive energy vector that can replace fossil fuel consumption, meeting global energy demands. To date, the most advanced method to produce green hydrogen is through water electrolysis using the residual supply of renewable energy. The current state-of-the-art catalysts used in electrolyzers are platinum-based metals and ruthenium/iridium oxides. The scarceness of these elements, combined with their high price, make these catalysts not economically viable for largescale production of hydrogen through water electrolysis. This study presents cobalt boride nanoflakes as materials to be used in both the anode and the cathode of an electrolyzer for electrochemical water splitting over a wide pH range. The cobalt boride nanoflakes were synthesized by the chemical reduction of CoCl2 using NaBH4 at three different concentrations to obtain CoB and Co2B nanoflakes. CoB nanoflakes exhibited both a higher specific surface area and greatest disparity in charge between B and Co, in comparison to Co2B. It was demonstrated that by tuning the properties of the cobalt boride nanoflakes, higher catalytic activities for both the hydrogen and oxygen evolution reaction can be achieved, showing good overall stability. [ABSTRACT FROM AUTHOR]

NiCo-based layered double hydroxides (NiCo-LDHs) have plenty of superior properties as electrode materials of supercapacitors, while the poor cycle performance heavily limits their application. An effective strategy to tackle this issue is to dope inactive Al that could stabilize the metallic layers to form ternary hydroxides. However, the desired ternary electrodes with appropriate content of Al3+ can hardly be prepared by conventional electrodeposition due to the great difference in solubility product constants (Ksp) of corresponding hydroxides, where the non-electroactive Al(OH)3 (Ksp = 1.3 × 10‒33) are preferentially deposited than the hydroxides of nickel and cobalt (Ksp = 2.0 × 10‒15, 1.6 × 10‒15). Here, we propose a novel electrodeposition method assisted by F‒ to control Al3+ content in NiCoAl-LDHs. By adjusting the concentration of F‒ in the electrolyte, Al3+ content, as well as the morphology and electrochemical performance of the electrodes, could be manipulated. With the optimum ratio of F− to Al3+, the as-obtained electrode shows high specific capacitance along with a long lifespan (54.1%, 10000 cycles). An asymmetric supercapacitor is assembled using active carbon as the negative electrodes, which displays the maximal energy density of 35.5 Wh kg−1 at the power density of 477.3 W kg−1, with a long lifespan (75%, 10000 cycles). [ABSTRACT FROM AUTHOR]

Copper (Cu), Nitrogen (N) Co-doped diamond-like carbon ((Cu:N)-DLC) films and Cu doped DLC (Cu-DLC) films were fabricated by high power impulse magnetron sputtering technique (HiPIMS). The influence of copper and nitrogen incorporation on the microstructure and electrochemical properties of Cu-DLC and (Cu:N)-DLC films were investigated by X-ray photoelectron spectroscopy, raman spectra and electrochemical workstation. The surface of all the films is cauliflower-like clusters, no obvious large particle Cu clusters can be observed. XRD patterns of theses films have only diffraction peak of copper and no other compounds. Raman spectra illustrate that Id/Ig varies from 2.79 to 3.01 as the N contents changes. XPS results identify that Cu does not form compounds or solid solution into DLC films. Electrochemical tests show that the electrode activity gradually increases with increasing the N contents of (Cu:N)-DLC electrode. Compared with (Cu:N)-DLC electrode, Cu-DLC electrode has a faster electron transfer rate (K0 is 1.88 × 10−2 cms−1 ), low transfer resistance (227.0 Ωcm² ), and a higher electrochemical activity (ΔEp is 93 mV). Consequently, the electrochemical properties of Cu doped DLC films are better than that of Cu, N co-doped DLC films. [ABSTRACT FROM AUTHOR]

Accurately quantifying applied potential is important to ensuring the comparability, accuracy, and precision of electrochemical studies. Reference electrodes (REs) enable knowledge/determination of the applied potential at electrodes in electrochemical systems. Ultimately, the choice of RE will depend on the particular requirements of a given electrochemical system, however, we note it is imperative to ensure the accuracy of the RE potential and its proper translation to a standardized scale. In this work, we highlight that while there are many commercially available REs, these must be experimentally calibrated to a reliable and practical standard potential scale, for instance the reversible hydrogen electrode (RHE) scale for aqueous systems. With representative data, we provide streamlined instructions on how to calibrate any RE to the RHE scale. We also provide guidance to mitigate and/or avoid possible electrolyte contamination issues arising from REs. Moreover, we offer a step-by-step guide on how to build a practical RHE RE, which may be a suitable and desirable option in certain applications. Our work emphasizes the need for the continuous adoption of standardized reference potential scales and demonstrates the versatility of the RHE scale, particularly in aqueous electrochemistry. [ABSTRACT FROM AUTHOR]

(Ba0.95La0.05)(Fe0.8Zn0.2)O3-δ (BLFZ) is a good candidate for protonic ceramic fuel cell cathodes owing to its high proton concentration and decent electronic conductivity. However, the poor catalytic activity of BLFZ limits the electrochemical reaction on the cathode surface, resulting in poor fuel cell performance in hydrocarbon fuels. In this study, to enhance the catalytic activity of BLFZ, Fe cations were substituted with cobalt (Co) cations to synthesize (Ba0.95La0.05)(CoxFe0.8-xZn0.2)O3−δ (BLCFZ) (x = 0–0.8). A single-phase perovskite structure was obtained when the mol% of Co (x) was 0.2 and 0.4, while secondary phases were observed at x = 0.6 and 0.8. The cathode performance was improved by doping Co into BLFZ. The polarization resistances of the fuel cell with BLCFZ (x = 0.2) in H2 and CH4 fuels at 600 °C were smaller than those of the fuel cell with BLFZ (x = 0) and the power density in H2 fuel at 600 °C increased from 0.7 to 0.9 Wcm−2 . Equivalent circuit models were used to analyze the contribution of Co in improving the catalytic activity of the cathode. [ABSTRACT FROM AUTHOR]

Since the double perovskite oxides Sr2Mg1-xMnxMoO6−δ were reported as anode materials for solid oxide fuel cells (SOFCs) by Professor Goodenough in 2006, they have attracted increasing interest in the past decades. The double-perovskite type oxide materials have been widely used as oxygen, fuel and symmetrical electrodes for electrochemical catalytic reaction. This article reviews the latest progress of double perovskite electrode materials in crystal structure, ion-electron conducting model, catalytic activity, degradation mechanism and optimizing strategies. Special attentions are paid to the double perovskite oxides used as oxygen, fuel and symmetrical electrodes. Their advantages, disadvantages and electrochemical performances as SOFC electrodes have been discussed through extensive analysis of the literatures. Particular emphasis has been directed towards basic principles and various affecting factors regarding the performance and stability for the double perovskite oxides and their composites. The solutions to overcome the drawbacks of double perovskite electrodes, including element substitution, defect engineering and so on, have also been demonstrated. [ABSTRACT FROM AUTHOR]

Lithium (Li) metal is considered an ideal anode material for Li-ion batteries. However, traditional carbonate-based solvents exhibit poor compatibility with the Li anode. High-concentration electrolytes (HCEs) are promising in the improvement of the behavior of the Li anode. To determine suitable HCE formulations, we revealed the effects of various carbonate solvents and Li salts in HCEs on the Li anode in terms of electrochemical performance, morphology, and surface chemical components. After screening six carbonates and four Li salts, the results suggested that ethylene carbonate (EC) and lithium bis(fluorosulfonyl)imide (LiFSI) were suitable in HCEs for the Li anode. The EC1–2 (molar ratio of LiFSI to EC is 1:2) electrolyte exhibited great cycling stability for up to 250 cycles at a high average Coulombic efficiency of 97.1% at a current density of 1 mA cm−1 with a fixed capacity of 0.5 mAh cm−2 . This was demonstrated as the formation of large Li with uniform nodule-like morphology and dense structure. In addition, the surface components on the Li anode were observed to have been highly contributed by the FSI-anion decomposition with the least EC reduction, providing an anion-derived surface with rich Li-F content. [ABSTRACT FROM AUTHOR]

This study was conducted to understand the effect of well-known water-washing process on Ni-rich LiNi0.885Co0.100Al0.015O2 (NCA) cathode material, which reduces the amount of residual lithium compounds in NCA to improve lithium-ion batteries (LIBs) characteristics. X-ray absorption fine structure (XAFS) analysis revealed that the oxidation state of the surface nickel in washed NCA particles was reduced. The fact was consistent with the increase in charge transfer resistance (Rct) measured by the electrochemical impedance spectroscopy (EIS) method. From X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses, it was found that the residual lithium compounds were washed away not only from the surface of NCA particles but also from grain boundaries or voids in between primary particles of NCA, by water-washing process. Differential scanning calorimetry (DSC) measurements suggested that an increase in specific surface area of NCA particles by water-washing was attributed a rapid heat release from the charged cathode material during heating to. On the other hand, cross-sectional scanning electron microscope (SEM) images showed that the crack formation inside washed NCA particles were suppressed after charge/discharge cycling. As a result, the capacity retention of washed NCA electrode at 60 °C cycling was improved. [ABSTRACT FROM AUTHOR]

In this work, the performance of commercial (250–300 mAh) Li1.11Ni0.34Mn0.53Al0.02O2/graphite (LNMA) and Li1.167Ni0.183Mn0.558Co0.092O2/graphite (LNMC) pouch cells was evaluated using different cycling drive profiles, temperatures, formation voltages, cycling upper and lower cut-off voltages. A variety of electrolyte additives and additive combinations were tested in the LNMA cells. The best performing electrolyte in high voltage LNMA cells (4.6 V upper cut-off) was Control + 2% fluoroethylene carbonate (FEC) + 1% lithium difluorophosphate (LFO) + 1% lithium difluoro(oxalato)borate (LiDFOB) with 87% capacity retention after 720 cycles. LNMA cells cycled to 4.25 V and LNMC cells cycled to 4.44 V at 40 °C were able to cycle for 1000 cycles before reaching 80% capacity. These materials can have surprisingly good high-voltage performance, but we stress that a fundamental breakthrough that can eliminate the voltage fade that is ubiquitous in Li-rich and Mn-rich materials is necessary to make Li-rich materials competitive with existing cell chemistries. We demonstrate that the high specific capacity of Li-rich materials can be deceptive when making conclusions about the energy density of Li-rich/graphite full cells. Hopefully, these results can set a baseline for other researchers in the Li-rich space. [ABSTRACT FROM AUTHOR]

Electrochemical performance of electrode in structural supercapacitor is much lower than that in common supercapacitor owing to solidification confinement of ions movement. Herein, NiCo2O4/reduced graphene oxide (rGO) nanosheets are firstly assembled with KOH/polyacrylic acid (PAA)/cement, LiOTf/PAA cement, KOH/polyethylene oxide (PEO) cement and LiOTf/PEO cement into four structural supercapacitors through hydration process. As the NiCo2O4 content in NiCo2O4/rGO composite exceeds 13 wt %, the areal capacitance of NiCo2O4/rGO electrode at high current densities decreases. The (13%) NiCo2O4/rGO electrode presents the best electrochemical performances with initial areal capacitance of 3.16 F cm−2 at 0.5 mA cm−2, capacitance retention rate of 61% after current density increasing by 80-fold and retention of 86.1% after 10000 cycles at 10 mA cm−2 . The corresponding four structural supercapacitors show superior electrochemical performances with areal capacitances of ∼ 330.4 mF cm−2, coulombic efficiencies of ∼ 100%, power densities of ∼ 2.7 mW cm−2 and energy densities of ∼ 0.64 mWh cm−2 . The electrochemical efficiencies of (13%) NiCo2O4/rGO electrodes in four structural supercapacitor devices are in the range of 0.16 ∼ 0.12, which are prominent in high-end structural supercapacitors. Thus NiCo2O4/rGO electrode is demonstrated to enhance the electrochemical matching with polymer cement electrolyte for structural supercapacitor. [ABSTRACT FROM AUTHOR]

Li- and Mn-rich layered oxides are a promising next-generation cathode active material (CAM) for automotive applications. Beyond well-known challenges such as voltage fading and oxygen release, their commercialization also depends on practical considerations including cost and energy density. While the cost requirement for these materials could be satisfied by eliminating cobalt, the volumetric energy density requirement might imply the transition from the most widely used porous structure to a more densely packed structure. Here, we investigated five Li- and Mn-rich layered oxides which were synthesized by various routes to obtain CAMs with different morphologies (porous vs dense), transition-metal compositions (Co-containing vs Co-free), and agglomerates sizes (≈6−12 μm). The as-received materials were characterized, e.g., by gas physisorption, Hg intrusion porosimetry, as well as X-ray powder diffraction, and were electrochemically tested by a discharge rate test. Thus, we identified two important material metrics which determine the initial electrochemical performance of Li- and Mn-rich CAMs, and which might be used as performance predictors: (i) the surface area in contact with the electrolyte that defines the effective current density which is applied to the surface of the CAMs, and (ii) the microstrain in the bulk that affects distinct redox features during cycling. [ABSTRACT FROM AUTHOR]

In this study, the influence of calendering and laser structuring on the pore structure and electrochemical performance of electrodes is reported. Graphite anodes of varying bulk porosity were micro structured with pulsed laser radiation. Using scanning electron microscopy and energy-dispersive X-ray spectroscopy, laser structuring was found to release superficial pore clogging caused by calendering and to result in binder agglomerates on the electrode surfaces. Structured electrodes showed higher porosities than their unstructured counterparts due to a thickness increase and material removal, but no significant change in the pore size distribution was detected using mercury intrusion porosimetry. Electrochemical impedance spectra of symmetric battery cells revealed increasing ionic resistances and tortuosities for decreasing electrode porosities. Laser structuring significantly reduced the underlying lithium-ion diffusion limitations at all porosity levels. In a discharge rate test, performance deteriorations at high currents were found to be amplified by calendering and could be diminished by electrode structuring. The performance improvements by laser structuring moved towards lower C-rates for stronger compressed anodes. Despite their growth in thickness and porosity, laser structured graphite anodes showed a higher volumetric energy density at high currents than unstructured electrodes, which demonstrates the potential of electrode structuring for highly compressed anodes. [ABSTRACT FROM AUTHOR]

It is well known that Pb(II) is considered a highly toxic metal. The slight difference between toxic and permissible levels in drinking water is a matter of concern; therefore, highly sensitive and selective techniques have been proposed for quantification, such as the electrochemical ones. In this work, an easy, simple, low-cost, and high selective sensor based on carbon paste electrodes (CPE) and ion-imprinted polymers (IIP) is proposed for Pb(II) analysis in real water samples. Recognition cavities, selective to Pb(II), were synthesized based on a cross-linked polymer using vinyl pyridine. A modified CPE was constructed by a mixture of graphite powder, IIP, and paraffin oil. By voltammetry studies, a notable difference was observed in the electrochemical response of the electrodes modified with IIP and those with non-imprinted polymer (NIP), confirming the existence of the recognition cavities in the IIP. The construction and analysis parameters related to the analytical response of Pb(II) (anodic current intensity of stripping voltammetry), were optimized; the selectivity was also studied considering potential interference ions. A linear concentration range from 3.3 mg l-1 to 33 mg l-1 and a limit of detection of 0.99 mg l-1 were achieved. Pb(II) was successfully quantified in real complex samples without previous treatment. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction reaction (CO2RR) has been studied in 0.1 M of KCl (pH of 6.96), NaHCO3 (pH of 8.3) and K2CO3 (pH of 11.36) cathodic solutions with various counter electrodes including graphite rod, SS316 rod and Pt mesh at different potential ranges on the Znx–Ni1-x bimetallic electrocatalysts. Among the Znx–Ni1-x electrocatalysts, the Zn–Ni electrode with a composition of 65 wt% Zn and 35 wt% Ni and cluster-like microstructure has the best performance for CO2RR by according to minimum coke formation and optimum CO and H2 faradaic efficiencies (CO FE% = 55% and H2 FE% = 45%). The cyclic voltammetry (CV) measurements and gas chromatography (GC) analysis for the CO2RR showed that KCl solution as the cathodic electrolyte with pH of 7 has the best performance and appropriate faradaic efficiency for H2(40%) and CO(30%) products in low potential value (−0.6 v) in this study. The best potential range for the CO2RR on the Zn-Ni bimetallic electrocatalyst in KCl solution with the scan rate (SR) 0.05 V. s−1 is between −0.3 V to −1 V vs Ag/AgCl. The use of stainless-steel electrode (SS316) as a counter electrode for electrochemical CO2RR is cost-effective and performs better than graphite electrode, but at high applied potential it oxidizes and dissolves in the electrolyte and then ions transfer to the Nafion membrane and poisons it. [ABSTRACT FROM AUTHOR]

This work presents a novel electrochemical sensor for methanol, based on a Cu(II) Metal-Organic Framework. The copper (II) benzenetricarboxylic metal-organic framework (Cu-BTC) was synthesized in mild condition at room temperature, and the obtained crystals were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The obtained Cu-BTC was incorporated at different ratios (7, 15, 30 wt%) in carbon paste electrodes to determine its electrocatalytic activity in the absence and the presence of methanol. The electrodes were characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). An anodic peak response toward methanol was observed at 1.25 V using 0.1 M NaOH as supporting electrolyte, with a maximum current density of 10 mA. Also, the oxidation signal of methanol in the presence of ethanol was studied by DPV. The quantitative analysis of methanol in the presence of ethanol using the modified electrode presented a LOD, LOQ and sensitivity values of 0.0511 mM, 0.1549 mM, and 19.8 mA mM-1 cm-2, respectively. The results demonstrated the high potential of Cu-BTC as part of electrochemical sensors for the determination of methanol in actual samples. [ABSTRACT FROM AUTHOR]

MOF derived porous carbon materials have emerged as a research hotspot in recent years due to its exceptional properties like high electrical conductivity, large specific surface area, presence of numerous accessible active sites, high porosity etc. which endows them with diverse applications. The unique properties associated with derived material are inherited from the precursor MOF and the provision of in situ heteroatom doping into the carbon structure further enhances its properties specific to diverse applications. In this review, we discuss the recent advancements in MOF derived carbon focusing on its properties and electrocatalytic applications. In the first part, an overview of the unique properties, methods to regulate the morphology and composition, and the structure of MOF derived carbon materials are discussed. Then, the application of MOF derived carbon as a promising electrode material for electrochemical sensing as well as electrocatalytic process focusing on OER and HER are explained in detail. Furthermore, the challenges that need to be addressed and future aspects of MOF derived carbon research are presented. [ABSTRACT FROM AUTHOR]

The resurgence of electromobility drives the need for high energy density cathode materials. LiNiO2 (LNO) meets this demand, based on its high specific capacity in a narrow voltage range and without relying on scare elements. Yet, it has been plagued by various issues, such as poor cycling performance and thermal instability. Adding dopants, such as widely available Mg2+, is a common strategy to balance cycling performance and energy density. Most prior studies focused on large Mg content ranges and were based on laboratory X-ray diffraction. Hence, the influence of Mg2+ addition on the crystal structure remains ambiguous, especially when small amounts are used (< 5 mol%; particularly interesting for industrial applications). Here, we present a systematic study of LiNi1-yMgyO2 (0 ≤ y ≤ 0.05) investigated by high-resolution synchrotron-based X-ray diffraction combined with elemental analysis, electron microscopy and electrochemical testing. The synthetic route relies on the addition of 10 nm Mg(OH)2 nanoparticles prior to the final calcination, as well as on co-precipitation. It is found that Mg2+ mostly occupies the Ni site until saturating at ~1.7%, then the Li site becomes preferred. This trend in the site occupancies influences the lattice parameters, oxygen coordinate within the unit cell and Ni-O bond distances. Doping also modifies the electrochemical behavior as a cathode material, stabilizing the capacity retention during cycling but sacrificing specific discharge capacity. Laboratory-based operando X-ray diffraction reveals that the increase in capacity retention is due to the suppression of the H2-H3 phase transition and interlayer distance collapse already in 3% Mg-doped LNO. The combination of structural and electrochemical characterization of doped LNO provides useful insights into the structural chemistry of the Mg2+ dopant and can serve as a starting point to understand Mg as a component in multiple dopant strategies for cathode material design and application. [ABSTRACT FROM AUTHOR]

Hard carbon is the most attractive anode material for electrochemical sodium/potassium-ion storage. The preparation of hard carbon spheres directly from the broad sources of biomass is of great interest but barely reported. Herein, we developed a simple two-step hydrothermal method to construct porous carbon microspheres directly from the original waste biomass of camellia shells. The porous carbon microspheres have high specific capacities of 250 mAh gâˆ'1 and 264.5 mAh gâˆ'1 at a current density of 100 mA gâˆ'1 for sodium-ion batteries and potassium-ion batteries, respectively. And it has excellent cycle stability for sodium ions and potassium ions outperforming most reported hard carbons, which is mainly attributed to the microporous structure and spherical morphology. The work paves a way to prepare porous hard carbon spheres directly from biomass for alkali metal-ion batteries. [ABSTRACT FROM AUTHOR]

In nanocomposite electrodes, besides the synergistic effect that takes advantage of the merits of each component, phase interfaces between the components would contribute significantly to the overall electrochemical properties. However, the knowledge of such effects is far from being well developed up to now. The present work aims at a mechanistic understanding of the phase interface effect in C@TiO2 coreâ€"shell nanocomposite anode which is both scientifically and industrially important. Firstly, amorphous C, anatase TiO2 and C@anatse-TiO2 electrodes are compared. The C@anatase-TiO2 shows an obvious higher specific capacity (316.5 mAh gâˆ'1 at a current density of 37 mA gâˆ'1 after 100 cycles) and Li-ion diffusion coefficient (4.0 × 10â€"14 cm2 sâˆ'1) than the amorphous C (178 mAh gâˆ'1 and 2.9 × 10â€"15 cm2 sâˆ'1) and anatase TiO2 (120 mAh gâˆ'1 and 1.6 × 10â€"15 cm2 sâˆ'1) owing to the C/TiO2 phase interface effect. Then, C@anatase/rutile-TiO2 is obtained by a heat treatment of the C@anatase-TiO2. Due to an anatase-to-rutile phase transformation and diffusion of C along the anatase/rutile phase interface, additional abundant C/TiO2 phase interfaces are created. This endows the C@anatase/rutile-TiO2 with further boosted specific capacity (409.4 mAh gâˆ'1 at 37 mA gâˆ'1 after 100 cycles) and Li-ion diffusion coefficient (3.2 × 10â€"13 cm2 sâˆ'1), and excellent rate capability (368.6 mAh gâˆ'1 at 444 mA gâˆ'1). These greatly enhanced electrochemical properties explicitly reveal phase interface engineering as a feasible way to boost the electrochemical performance of nanocomposite anodes for Li-ion batteries. [ABSTRACT FROM AUTHOR]

Anode materials based on lithium titanate (LTO)/graphene composites are considered as ideal candidates for high-rate lithium-ion batteries (LIBs). Considering the blocking effects of graphene nanosheets in electrodes during ion-transfer processes, construction of LTO/graphene composite structures with enhanced electrical and ionic conductivity via facile and scalable techniques is still challenging for high-rate LIB. In this work, structures of anode materials based on LTO nanoplates embedded with graphene quantum dots (GQDs) are demonstrated for high-rate LIB. The hybrids can be facilely prepared via in situ introduction of GQDs during the process LTO preparation, which enables a uniform dispersion of GQDs within LTO. This method is convenient, rapid, and can be easily scaled-up. The introduction of 0.05 wt.% GQDs can greatly enhance the electrochemical performance of the electrodes. The electrodes with 0.05 wt.% GQDs deliver a specific discharge capacity of 185, 181 and 179 mAh gâˆ'1 at 5, 10, and 20 C, respectively. The performance enhancement is suggested to be due to the synergistic interactions between LTO and GQDs. The strategy as well as as-designed structures of LTO/GQDs show potentials for application as high-rate anode materials in LIBs application. [ABSTRACT FROM AUTHOR]

In this work, a novel Ni/ZnO-MnO2 electrode was fabricated by utilizing spent zinc-manganese batteries and then was applied to the electrochemical treatment of ammonia-containing wastewater. The obtained Ni/ZnO-MnO2 electrode was characterized by scanning electron microscopy, X-ray diffraction, and linear scanning voltammetry, suggesting that the fabricated electrode had a flower-like structure and showed high oxygen evolution potential and electrochemical activity. The electrochemical performance of the ZnO-MnO2 electrode in regard to ammonia removal and product selectivity was then investigated with different operating factors (i.e., electrolyte concentration, initial pH value, current density, and Cl- concentration), and the results indicated that the ammonia removal efficiency could reach 100% with a N2 selectivity of 91.8% under optimal conditions. Additionally, the mechanism of ammonia oxidation was proposed by cyclic voltammetry tests and active radical measurements, showing that ammonia was mainly oxidized via direct electron transfer, hydroxyl radicals, and active chlorine. Finally, the ZnO-MnO2 electrode was equipped for the treatment of actual pharmaceutical wastewater, results for which showed that ammonia could be completely removed with a current efficiency of 26.2% and an energy consumption of 52.7 kWh/kg N. Thus, the ZnO-MnO2 electrode prepared by recycling spent batteries is a promising anode for wastewater treatment. [ABSTRACT FROM AUTHOR]

Ni-rich lithium nickel manganese cobalt oxides have been extensively studied as high capacity and low cost positive electrode materials for lithium-ion batteries. In order to improve their electrochemical properties, especially cycle capability, we develop a surface modification on single polycrystalline particles of LiNi0.6Mn0.2Co0.2O2 (NMC622) powder with a lanthanum-based oxide. A wet-chemical process and following heat-treatment at 750 °C produce K2NiF4-type La2Ni0.5Li0.5O4 nanoparticles on the surface of NMC622 particles. The La2Ni0.5Li0.5O4-modification improves capacity retention of NMC622 during long-term chargedischarge cycling in the wide voltage range of 3.0-4.5 V at room temperature. The capacity retention at the 150th cycle is about 86% (from 182 to 157 mAh g-1) which is higher than 78% (from 176 to 135 mAh g-1) obtained for the unmodified NMC622 electrode. Further improvements by the La2Ni0.5Li0.5O4 modification are confirmed in the capacity retention cycled at 60 °C and in the discharging rate capability. The La2Ni0.5Li0.5O4-modification is highly effective on the single polycrystalline particles of Nirich NMC for long cycle-life and high-rate lithium-ion batteries. [ABSTRACT FROM AUTHOR]

High energy-density supercapacitors (SCs) with long operating life, cost-effective, and competitive cycling performance is attracted great research attention to competing in the requirements of the modern age. However, despite these benefits, SC hampers inadequate rate-capability and structural deterioration, which primarily affects its commercialization. Herein, ultra-thin two-dimensional (2D) ZnCo2O4 nanosheets are in situ anchored on the conductive surface of nickel foam (denoted as ZCO@NF) by hydrothermal process. The binder-free ZCO@NF is employed as an electrode for SCs and shows impressive charge storage properties. ZCO@NF electrode exhibited a high capacitance of 1250 (750) and 733 F g−1 (440 C g−1) at 2.5 and 20 A g−1, respectively, demonstrating the outstanding rate-capability of 58.6% even at 8 times larger current density. Furthermore, the ZCO@NF electrode exhibits admirable capacitance retention of 96.5% after 10 000 cycles. This impressive performance of the ZCO@NF electrode is attributed to the high surface area which gives a short distance for ion/electron transfer, a high conductivity with extensive electroactive cities, and strong structural stability. The binder-free approach provides a strong relationship between the current collector and the active material, which turns into improved electrochemical operation as an electrode material for SCs. [ABSTRACT FROM AUTHOR]

The electrooxidation of glycerol was studied on monometallic (Pt/C, Co/C, Ni/C, Cu/C) and bimetallic catalysts (PtCo/C, PtNi/C, PtCu/C) - containing porous carbon cloth electrodes in an alkaline medium to gain insight about the potentials of electrodes for simultaneous hydrogen and chemical production. Physical and chemical properties of catalysts were characterized by using X-ray diffraction, X-ray photoemission spectroscopy, and transmission electron microscopy while electrochemical characteristics of electrodes were investigated by cyclic voltammetry, choronoamperometry, and electrochemical impedance spectroscopy. Bimetallic catalysts-containing electrodes showed higher glycerol electrooxidation activities and stabilities compared to monometallic catalysts-containing electrodes. The highest activity was observed on the PtCu/C-containing electrode due to its higher electrochemical active surface area and low kinetic and mass transfer resistance. It was also found that the presence of porous carbon cloth had a considerable effect on the glycerol electrooxidation activity. [ABSTRACT FROM AUTHOR]

Recently, electrochemical sensors have been applied for the detection of heavy metal ions. The modifier on the electrochemical electrode is the key factor for enhanced performance. Modification by combining metal oxide nanomaterials with good adsorption property and graphene oxide (GO) with good conductivity can construct a useful sensing interface to detect heavy metal ions. Here, the effects of structures and morphologies of Co3O4/GO composite modifiers on the electrochemical detection performance were studied. The results show that Co3O4/GO composite with holey nano-sheets of pure Co3O4 on lamella GO substrate had the best electrochemical performance for their large active sites and enhanced ion and charge transports. The limits of detection of the electrochemical sensors based on developed Co3O4/GO composite to Cd2+ and Pb2+ were calculated as 57 and 29.4 nM, respectively, which are lower than the guideline values recommended by the World Health Organization for drinking water. Furthermore, the designed sensor also showed excellent stability, selectivity, and acceptable reproducibility and reliablity. The results indicate that Co3O4/GO composite with holey layer structures as a promising electrode modifier could be potentially applied in the electrochemical detection of heavy metal ions on-site. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable sodium-ion batteries (ARSBs) have received much attention due to their low cost, the vast abundance of sodium, and the possible application for a smart grid-scale energy storage system. Here, we synthesized Na3FePO4CO3, a cathode material for ARSBs by a low-temperature ionothermal method using deep eutectic solvent and investigated its electrochemical performance. The physical characterization of the synthesized cathode material was done using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetry analysis, differential thermal analysis, and X-ray photoelectron spectroscopy to evaluate crystal size, structure, elemental composition, morphology, and oxidation state. The electrochemical behavior of Na3FePO4CO3 in 2 M Na2SO4 was studied using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge techniques. The study revealed that at high current rates, the synthesized cathode material, Na3FePO4CO3 exhibited excellent electrochemical performance. The full cell NaTi2(PO4)3/2 M Na2SO4/Na3FePO4CO3 delivers a discharge capacity of 78.6 mAh g-1 at C/5 rate which is 82% of the theoretical capacity (96 mAh g-1 for one-electron reaction) and 41.62 mAh g-1 at 2 C rate Further, it retains a discharge capacity of 70 mAh g-1 over 100 cycles with good cyclability. [ABSTRACT FROM AUTHOR]

This paper develops a three-dimensional, transient, chemo-mechanical model that predicts the performance of single secondary particle Li-ion battery cathodes. The secondary particles are composed of numerous (approximately 60) randomly oriented singlecrystal primary particles. The model incorporates concentration-dependent and anisotropic material properties. As much as possible, electrochemical, transport, and structural properties for crystalline NMC811 (LixNi0.8Mn0.1Co0.1O2) are taken from prior publications. Weak Van der Waals bonding between primary particles is modeled empirically using a spring analogy, which enables local primary-particle separations (disintegration) and subsequent reattachments. The model fully couples Li diffusion and the mechanical response. Results include predictions of local Li-concentrations and stresses. High stresses are found near grain boundaries, especially when the lattice orientations are greatly misaligned. Particle separations are characterized in terms of a damage parameter. The model is used to predict the effects of design and operating conditions, including charge/discharge rates, cycling scenarios, and particle sizes. [ABSTRACT FROM AUTHOR]

Metal sulfides are often used as cathode materials for lithium-ion batteries (LIBs) owing to their high theoretical specific capacity; however, excessively fast capacity decay during charging/discharging and rapid shedding during cycling limits their practical application in batteries. In this study, we proposed a strategy using plasma treatment combined with the solvothermal method to prepare cobalt sulfide (Co1−xS)-carbon nanofibers (CNFs) composite. The plasma treatment could introduce oxygen-containing polar groups and defects, which could improve the hydrophilicity of the CNFs for the growth of the Co1−xS, thereby increasing the specific capacity of the composite electrode. The results show that the composite electrode present a high discharge specific capacity (839 mAh g−1 at a current density of 100 mA g−1) and good cycle stability (the capacity retention rate almost 100% at 2000 mA g−1 after 500 cycles), attributing to the high conductivity of the CNFs. This study proves the application of plasma treatment and simple vulcanization method in high-performance LIBs. [ABSTRACT FROM AUTHOR]

The application of natural materials films for the surface modification of glassy carbon and gold electrodes to enhance their selective sense in the electrochemical detection of organic and inorganic species is a major challenge. In this study, gliadin was extracted from wheat flour and, for the first time, applied as a novel biocompatible permselective modifier film on gold and glassy carbon electrodes for the electrochemical detection of various compounds. The structure and surface morphology of the extracted gliadin were investigated by Fourier transform infrared (FT-IR) spectroscopy and atomic force microscopy (AFM) techniques. AFM and scanning electron microscopy (SEM) showed that porous structures with high nanometric roughness were present in gliadin membranes prepared from the casting solution of gliadin in ethanol. Compared to hydrophobic ions, the capacitance (C) values of electrical double layers of gliadin film modified electrodes for hydrophilic ions were very high. The findings of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) proved high performance of gliadin membrane as permselectcive film for nominated cationic compounds with fast electrochemical kinetics responses in aqueous solutions (PBS, pH = 7). This behavior was verified by circulating solutions containing model compounds from a home-made continuous cell equipped with gliadin-modified polyamide membranes. [ABSTRACT FROM AUTHOR]

The specific capacity of Ni rich LiNixCoyMnzO2 (x > 0.5) cathodes is higher as their Ni content is higher and can reach values up to 240 mAh g-1 (x-1) while being charged below 4.3 V vs Li. This property is very important since charging Li-ion batteries below this potential is not detrimental to anodic stability of the electrolyte solution. However, as the content of Ni increases, the electrochemical, structural and thermal stability decreases. Here we focus on LiNi0.85Co0.1Mn0.05O2 which was stabilized by doping it withW by a simple solid-state method. This doping greatly improved the electrochemical, thermal and structural stability, although both X-ray diffraction and density functional theory (DFT) studies indicated negligible change in the structural parameters upon doping. For example, 96% capacity retention was achieved for doped cathodes after 120 cycles at 45 °C vs Li anodes, compared to 80% capacity retention for an undoped, reference cathode. Cross sectioning studies of cycled cathodes by SEM imaging of FIB-cut samples confirmed the correlation between structural and electrochemical stability. W-doping stabilizes the cathode material by reducing the formation of cracks and loss of the spherical shape of the active mass particles, upon prolonged cycling. Additionally, W-doping enhances the thermal stability of the cathode material. DFT based calculations indicated that doping this cathode material with tungsten, reduces the amount of Jahn-Teller active Ni3+ ions within the crystal lattice and introduces strong W-O bonds, which stabilize the active mass during repeated lithiation--lithiation cycling. [ABSTRACT FROM AUTHOR]

Mechanical degradation is a major cause of electrochemical instability of "layered"/"cation-ordered" Li-transition metal (TM) oxides, but with the focus so far being directed mainly to deep delithiation states of Ni-containing Li-TM-oxides. By contrast, our operando stress measurements during galvanostatic cycling of LiCoO2 (viz., the base Li-TM-oxide) has revealed that mechanical instability can be initiated even during the initial stages of delithiation, especially upon initiation/propagation of "HI - HII" phase transformation, starting at ~3.8 V vs Li/Li+ [as partly reported in, Malav et al., ECS Electrochem. Lett., 4(12), A148 (2015)]. "Flattening"/"plateauing" of overall/average in-plane stress build-up in the operando stress profiles is a signature of the same. In a bid to further understand and throw new insights onto such electro-chemo-mechanical responses, the present work develops a mathematical model that includes in-plane extension/bending to signify (de)lithiation-induced deformation, concentration-triggered phase transformation and, more importantly, concepts associated with transformation induced plasticity. Internal stress build-up during "HI - HII" phase transformation of LiCoO2 is predicted to be a likely cause for plastic deformation. Overall, the model is able to capture the initial monotonic stress build-up, followed by "plateauing" during phase transformation, and reaffirms a strong correlation between phase transformations, transformed phases and accompanying mechanical stresses during electrochemical delithiation/lithiation of Li-TM-oxide. [ABSTRACT FROM AUTHOR]

Fast charging is one of the main challenges of electric vehicles, partly due to electrolyte transport limitations across porous electrodes in Li-ion cells. The determination of electrolyte transport properties is crucial for modeling fast charging and adjust cell design accordingly. In this work, diffusion coefficient and cation transference number for a 1 M LiPF6 in ethylene carbonate/diethyl carbonate mixture (1:1 in weight) are determined using a multireference electrode electrochemical cell (four herein). It is an extension of the work by Farkhondeh et al. [J. Phys. Chem. C 2017, 121, 8, 4112-4129] that was based on two reference electrodes. Long galvanostatic pulses allow for building up concentration gradients across the cell (restricted diffusion), which are subsequently let to relax under open circuit. The multiple voltages (three herein) measured between the four reference electrodes are simultaneously analyzed with four different procedures that involve a combination of analytic methods and nonlinear regression of the data with a numerical model. The parameter mean values and 95%-confidence intervals are evaluated using Student t-distribution and the bootstrap method. Values reported by combining all methods together are: D = 2.62 × 10-10 [± 2.29 %] m2 s-1, + = [± ] t 0 0.204 12.25 % at 25 °C. [ABSTRACT FROM AUTHOR]

Tin and its oxides are promising anode materials owing to their high theoretical capacity, rich resource, and environmental benignity. To achieve low cost and green synthesis, a facile synthetic route of SnOx/graphene composites is proposed, using a simple galvanic replacement method to quickly obtain abundant foamed tin as raw material and ball milling method to realize a mechanochemical reaction between SnOx (0 ≤ x ≤ 2) and graphene. Under different annealing conditions, the foamed tin is converted to tin oxides with multiple oxidation states (Sn3O4, SnO, and SnO2). These unique components can greatly affect the electrochemical performance of the electrode in LIBs. The as-prepared electrode (SnOx-300/G) obtained by annealing foamed tin at 300 °C for 4 h and combining SnOx powders with graphene via ball milling shows great cycling stability, retaining a high capacity of 786 mA h g−1 at 0.1 A g−1 after 150 cycles, and its initial Coulombic efficiency can reach 84.03%. Thus, this facile synthesis can provide an environmentally friendly route for commercial production of high-performance energy storage materials. [ABSTRACT FROM AUTHOR]