Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

Microstructure and electrochemical properties of melt-spun Nd_(0.8)Mg_(0.2)(Ni_(0.8)Co_(0.2))_(3.8) hydrogen storage alloy

The effects of rapid solidification on the microstructure and electrochemical properties of Nd0.8Mg0.2(Ni0.8Co0.2)3.8 alloy were systematically investigated.The microstructure of alloys was characterized by scanning electron microscopy(SEM),X-ray diffractometer(XRD) and transmission electron microscopy(TEM).It was found that the melt-spun Nd0.8Mg0.2(Ni0.8Co0.2)3.8 ribbons became thinner and the average grain size of the ribbons became smaller with increasing wheel speed.A fraction of amorphous phase was observed for the ribbons melt-spun at high wheel speed(≥20 m/s).Microstructural characterization revealed that two phases:(Nd,Mg)2(Ni,Co)7 main phase(Ce2Ni7 type structure) and NdNi5 second phase(CaCu5 type structure),existed in the samples in cast state and melt-spun.The cycle stability of the melt-spun alloys was significantly enhanced as compared with cast alloy,and the sample prepared at wheel speed of 20 m/s exhibited good comprehensive electrochemical properties.

Electrochemical preparation and performance of γ-MnO_2

The effects of the electro-deposition conditions on the crystal structure and the properties of electrolytic manganese dioxide(EMD) were investigated in this paper. The results show that EMD was γ-crystal, with sand-like rough interface. The optimal preparation conditions of EMD were 30 min deposition time, and p H=1.0 in Mn SO4-H2SO4 solution at 50 ?C. Surfactant(P1) was conducive to the uniform and stable surface of γ-Mn O2 film, the impedance and the specific surface area of the electrode modified with γ-Mn O2 increased by 21.4 times and 75.6 times, respectively. The redox reversibility and the resolution ratio of characteristic peaks with the modified electrode were significantly improved in the benzodiazepines electrochemical reaction. The achievement illustrated that the controllable synthesis of γ-Mn O2 film thickness was practical in electrochemical sensors, and the determination reliability of benzodiazepines was improved with γ-Mn O2 modified electrodes used in environment monitoring technology.

Carbon-coated manganese dioxide nanoparticles and their enhanced electrochemical properties for zinc-ion battery applications

In this study, we report the cost-effective and simple synthesis of carbon-coated α-MnO_2nanoparticles(α-MnO_2@C) for use as cathodes of aqueous zinc-ion batteries(ZIBs) for the first time. α-MnO_2@C was prepared via a gel formation, using maleic acid(C_4H_4O_4) as the carbon source, followed by annealing at low temperature of 270 °C. A uniform carbon network among the α-MnO_2 nanoparticles was observed by transmission electron microscopy. When tested in a zinc cell, the α-MnO_2@C exhibited a high initial discharge capacity of 272 m Ah/g under 66 m A/g current density compared to 213 m Ah/g, at the same current density, displayed by the pristine sample. Further, α-MnO_2@C demonstrated superior cycleability compared to the pristine samples. This study may pave the way for the utilizing carbon-coated MnO_2 electrodes for aqueous ZIB applications and thereby contribute to realizing high performance eco-friendly batteries.

The effect of welding materials on 1Cr18Ni9Ti and 2Cr13 steel welded joints electrochemical properties

By method of TIG,two kinds of welding materials were filled in and under certain welding craft conditions,1Cr18Ni9Ti and 2Cr13 were welded.The microstructure of two kinds of welded joints were observed and analyzed by OM,SEM.Through seawater immersion test,polarization curves and AC impedance spectroscopy of two kinds of welding joints were obtained.The results show that 2Cr13 and 1Cr18Ni9Ti welded joints are typical columnar crystal,the microstructure is lath martensite+austenite+carbide.The welded joints that filled in 308 and H1Cr21Ni10Mn7Mo welding wires,corrosion resistance has same change rule:Austenite base metal>HAZ near Austenite>welded joint>HAZ near Martensite>Martensite base metal.The every zone contrast of two kinds of welded joint corrosion resistance obtains:the welded joints filled in 308>the welded joints filled in H1Cr21Ni10Mn7Mo.

Oleic acid-treated synthesis of MnO@C with superior electrochemical properties

MnO@C nanocomposites are synthesized by annealing MnO microspheres treated with oleic acid as carbon source. The obtained MnO@C nanocomposites exhibit a discharge capacity of 1075 m Ah/g for the initial cycle, and show the excellent cycling performance with a discharge capacity of 421 mAh/g after100 cycles at a current density of 100 mA/g. The total specific capacity of MnO@C nanocomposites is higher than those of pure MnO microspheres in our experiments. Owing to the superior electrochemical behavior, the as-obtained MnO@C nanocomposites are potentially applied as next-generation anode material for lithium-ion batteries.

Electrochemical properties of Ca-Pb electrode for calcium-based liquid metal batteries

The Ca-Pb electrode couple is considered to be one of the least expensive(~36$/(k W·h))among various optional materials for liquid-metal batteries(LMBs).The electrochemical properties of Ca-Pb alloy in a Ca|Li Cl-Na Cl-Ca Cl_(2)|Pb cell were investigated in this paper.The electrode potential maintained a linear relationship in the current density range of 50-200 m A·cm^-2,which indicates that the alloying and dealloying processes of Ca with Pb attained rapid charge transfer and mass transport in the interface between the liquid electrode and electrolyte.The Ca-Pb electrode exhibited remarkable properties with a high discharge voltage of 0.6 V,a small self-discharge current density(<2 m A·cm^-2 at 600℃),and a high coulombic efficiency(>98.84%).The postmortem analysis showed that intermetallics Ca Pb3 and Ca Pb were uniformly distributed in the electrode with different molar fractions of Ca,which indicates that the nucleation of solid intermetallics did not hinder the diffusion of Ca in the electrode.This investigation on Ca-Pb electrode sheds light on the further research and the design of electrodes for Ca-based LMBs.

Study on Electrochemical Properties of MnO2/MoS2 composites

1 Introduction Supercapacitor also called electrochemical capacitor,has become one of the most promising energy storage devices due to its long service life,great power density,high energy density,green environmental protection(Simon et al,2008;Ma et al,2013).Based on the charge storage mechanisms,Supercapacitors can be divided

Nd–Mg–Ni alloy electrodes modified by reduced graphene oxide with improved electrochemical kinetics

To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g^(–1) increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.

Hierarchical Co3O4 Microstructures Decorated with Ag and Cu Oxides： Study of Photocatalytic and Electrochemical Properties

Three-dimensional hierarchical Co_3O_4 microstructures decorated with Ag and Cu oxides were prepared via displacement reaction and subsequent annealing treatment.Photocatalytic properties measurements revealed that the photocatalystic activities of Cu O/Co_3O_4 composites(Co_3O_4 microstructures decorated with Cu O)were enhanced while those of Ag_2O/Co_3O_4 composites(Co_3O_4 microstructures decorated with Ag_2O)were reduced,when compared with those of pure hierarchical Co_3O_4 microstructures toward the degradation of methyl orange.In addition,Cu O/Co_3O_4 composites exhibited an excellent recyclability ability of photodegradation.The electrochemical properties test indicated that both of the composite oxide electrodes exhibited excellent pseudocapacitive performance with relatively high specific capacitance and good long-term cycling stability.With the increase of the loaded Ag_2O and Cu O dosages deposited on the Co_3O_4 microstructures surface,the specific capacitance values of the composites were increased.Ag_2O/Co_3O_4 composite electrodes showed higher specific capacitance values and better cycling stability than Cu O/Co_3O_4 composite ones.

A New Mn(Ⅱ)Coordination Polymer Based on 1H-pyrazolo[3,4-b]pyridin-3-amine:Crystal Structure,Magnetic and Electrochemical Properties

A new polymer formulated as [Mn_3(1,3-BDC)_3(L)(H_2O)_3](1) based on linear trinuclear unit Mn_3(COO)_6 has been synthesized under solvothermal conditions with 1,3-benzenedicarboxylic acid(1,3-H_2BDC) and 1H-pyrazolo[3,4-b]pyridin-3-amine(L) as ligands. The polymer was characterized by the single-crystal X-ray diffraction analysis, infrared spectra, elemental analyses, power X-ray diffraction and TG analysis. It crystallizes in orthorhombic system, space group Pna21, with a = 7.9252(3), b = 17.9740(8), c = 22.3027(10) ?, Mr = 845.35, Z = 4, V = 3177.0(2) ?3, F(000) = 1708, D_c = 1.767 g/cm^3, μ(Mo Kα) = 1.257 mm^(-1), the final refinement give R = 0.0388 and w R = 0.0955 for 5595 reflections with I > 2σ(I). The polymer 1 can be symbolized as a pcu topology based on the Mn_3(COO)_6 as a secondary building unit. Furthermore, the magnetic properties and electrochemical properties of 1 are also investigated.

Synthesis, Crystal Structure and Electrochemical Properties of 2-Chlorobenzaldehyde Thiosemicarbazone

The title compound crystallized in space group P21/c with Z=4, in a unit cell ofdimensions. a=12.964(4), b=5. 131(5), c=14.970(1)A, V=9331 (1) A3, Dc=1 .429gcm",P=0.541mm-1, R=0.045, Rw=0.059. The equilibrium constant of the ligand with CdBr2 wasobtained by polarograPhic method. Crystal structufe determination revealed that the molecule is intransconformation and non-hydrogen atoms of the molecule are in one plane except N(3) atom.

Morphological and Electrochemical Characterization of Ti/MxTiySnzO2 (M = Ir or Ru) Electrodes Prepared by the Polymeric Precursor Method

This paper describes the effect of the composition of the oxide films on the properties of electrodes Ti/MxTiySnzO2 (M = Ir or Ru) prepared by the polymeric precursor method. XRD studies showed that the anodes are formed by solid solutions. The electrodes containing IrO2 exhibit lower activity for the oxygen evolution reaction. The doping of the electrode surface with SnO2 improves the catalytic properties of the anodes. However, it should be held in appropriate compositions, because the change in the atomic ratio of this element shows a marked effect on the stability of the oxides. Electrode Ti/Ir0.2Ti0.3Sn0.5O2 has lower lifetime, i.e. 6 hours. The 20% decrease in the stoichiometric amount of SnO2 increases the time to a value above 70 hours, as observed for Ti/Ir0.3Ti0.4Sn0.3O2. Electrode Ti/Ru0.3Ti0.4Sn0.3O2 shows lifetime of 11 hours;therefore IrO2 is more stable than RuO2 under the conditions investigated. These results suggest that electrode Ti/Ir0.3Ti0.4Sn0.3O2 is promising for different applications, such as water electrolysis, capacitors and organic electrosynthesis.

Zinc–Bromine Rechargeable Batteries:From Device Configuration,Electrochemistry,Material to Performance Evaluation

Zinc–bromine rechargeable batteries(ZBRBs)are one of the most powerful candidates for next-generation energy storage due to their potentially lower material cost,deep discharge capability,non-flammable electrolytes,relatively long lifetime and good reversibility.However,many opportunities remain to improve the efficiency and stability of these batteries for long-life operation.Here,we discuss the device configurations,working mechanisms and performance evaluation of ZBRBs.Both non-flow(static)and flow-type cells are highlighted in detail in this review.The fundamental electrochemical aspects,including the key challenges and promising solutions,are discussed,with particular attention paid to zinc and bromine half-cells,as their performance plays a critical role in determining the electrochemical performance of the battery system.The following sections examine the key performance metrics of ZBRBs and assessment methods using various ex situ and in situ/operando techniques.The review concludes with insights into future developments and prospects for high-performance ZBRBs.

Fiber swelling to improve cycle performance of paper-based separator for lithium-ion batteries application

It is well established that paper-based separators display short-circuit risk in lithium-ion batteries due to their intrinsic micron-sized pores.In this research,we have adjusted pore structure of paper by fiber swelling in liquid electrolyte.Specifically,the paper-based separator is prepared by propionylated sisal fibers through a wet papermaking process.Scanning electron microscope(SEM)and multi-range X-ray nano-computed tomography(CT)images display strong swelling of modified fibers after electrolyte absorption,which can effectively decrease the pore size of separator.Due to the high electrolyte uptake(817 wt%),paper-based separator exhibits ionic conductivity of 2.93 mS cm^(-1).^(7)Li solid-state NMR spectroscopy and Gaussian simulation reveal that the formation of local high Li^(+)ion concentration in the separator and its low absorption energy with Li^(+) ion(62.2 kcal mol^(-1))is conducive to the ionic transportation.In particular,the assembled Li/separator/LiFePO_(4) cell displays wide electrochemical stability window(5.2 V)and excellent cycle performance(capacity retention of 96.6%after 100 cycles at 0.5C)due to the reduced side reactions as well as enhanced electrolyte absorption and retention capacity by propionylation.Our proposed strategy will provide a novel perspective to design high-performance biobased separators to boost the development of clean and sustainable energy economy.

Dual-salt assisted synergistic synthesis of Prussian white cathode towards high-capacity and long cycle potassium ion battery

Prussian blue analogues(PBAs) are considered as superior cathode materials for potassium-ion batteries(PIBs) because of their three-dimensional open framework structure,high stability,and low cost.However,the intrinsic lattice defects and low potassium content typically results in poor rate and cycling performance,thus limited their practical applications.In this work,high-quality K1.64FeFe(CN)6(PW-HQ)material with less crystalline water(6.21%) and high potassium content(1.64 mol^(-1)) was successfully synthesized by a novel coprecipitation method with potassium citrate(K-CA) and potassium chloride(KCl) addition.Specifically,the electrode delivers a reversible capacity of 113.1 mA h g^(-1)at the current rate of 50 mA g^(-1)with~100% coulombic efficiency.Besides,the electrode retained 90% reversible capacity at 500 mA g^(-1)current density after 1000 cycles,indicating only 0.01% capacity decay per cycle.Moreover,we have revealed that the introduction of K-CA controlled the chelating rate of Fe(Ⅱ) and the addition of KCl increased the K+content,hence improving the capacity and stability of the asprepared electrodes.Structural evolution and potassium storage mechanism were further investigated by detailed ex-situ X-ray diffraction and in-situ Raman measurements,which demonstrated reversible potassiation/depotassiation behavior and negligible volume change during the electrochemical process.In general,this work provides an efficient strategy to eliminate water contents in Prussian blue cathode and improve its electrochemical performance,which plays a key role in promoting the industrialization of potassium ion batteries.

Chemical Oxidation Effects on Anion Exchange and Nitrate Sorption Capacity of Biochar for Ruminal Methanogenesis Inhibition

The chemical composition of biochar is determined by the chemical profile of the material the by-product is made of and the pyrolysis conditions. Analysis of commercial biochar detected similarities to the chemical profile of hardwood, which was used as an object of pyrolysis for biochar production and showed the presence of bridge-forming cations, such as manganese, iron, and sodium. Despite frequently being reported in existing literature, the current study showed that the redox potential of biochar is not associated with biochar’s ability to recover certain anions. No association was detected between biochar’s redox potential and the material nitrate sorption capacity. In fact, higher redox potential values were associated with lower nitrate absorption. In the case of the anion exchange capacity of biochar, a direct association between this electrochemical property of the by-product and its redox potential was observed. However, redox potential’s impact on anion exchange capacity can be inhibited by the presence of organic compounds in biochar’s chemical profile. The chemical oxidation of biochar is a complex process and is a research priority for a potential role to mitigate enteric methanogenesis in livestock.

High-Performance Li-ion Batteries and Super-capacitors Based on Prospective 1-D Nanomaterials

One-dimensional（1-D） nanomaterials with superior specific capacity, higher rate capability, better cycling peroperties have demonstrated significant advantages for high-performance Li-ion batteries and supercapacitors. This review describes some recent developments on the rechargeable electrodes by using 1-D nanomaterials（such as Li Mn2O4 nanowires, carbon nanofibers, Ni Mo O4 · n H2O nanorods, V2O5 nanoribbons,carbon nanotubes, etc.）. New preparation methods and superior electrochemical properties of the 1-D nanomaterials including carbon nanotube（CNT）, some oxides, transition metal compounds and polymers, and their composites are emphatically introduced. The VGCF/Li Fe PO4/C triaxial nanowire cathodes for Li-ion battery present a positive cycling performance without any degradation in almost theoretical capacity（160 m Ah/g）.The Si nanowire anodes for Li-ion battery show the highest known theoretical charge capacity（4277 m Ah/g）,that is about 11 times lager than that of the commercial graphite（372 m Ah/g）. The SWCNT/Ni foam electrodes for supercapacitor display small equivalent series resistance（ESR, 52 m?） and impressive high power density（20 k W/kg）. The advantages and challenges associated with the application of these materials for energy conversion and storage devices are highlighted.

Nanostructured Mn-based oxides as high-performance cathodes for next generation Li-ion batteries

Mn-based oxides have been regarded as a promising family of cathode materials for high-performance lithium-ion batteries,but the practical applications have been limited because of severe capacity deterioration(such as Li Mn O_(2)and Li Mn_(2)O_(4))as well as further complications from successive structure changes during cycling,low initial coulombic efficiency(such as Li-rich cathode)and oxidization of organic carbonate solvents at high charge potential(such as Li Ni0.5 Mn1.5 O4).Large amounts of efforts have been concentrated on resolving these issues towards practical applications,and many vital progresses have been carried out.Hence,the primary target of this review is focused on different proposed strategies and breakthroughs to enhance the rate performance and cycling stability of nanostructured Mn-based oxide cathode materials for Li-ion batteries,including morphology control,ion doping,surface coatings,composite construction.The combination of delicate architectures with conductive species represents the perspective ways to enhance the conductivity of the cathode materials and further buffer the structure transformation and strain during cycling.At last,based on the elaborated progress,several perspectives of Mn-based oxide cathodes are summarized,and some possible attractive strategies and future development directions of Mn-based oxide cathodes with enhanced electrochemical properties are proposed.The review will offer a detailed introduction of various strategies enhancing electrochemical performance and give a novel viewpoint to shed light on the future innovation in Mn-based oxide cathode materials,which benefits the design and construction of high-performance Mn-based oxide cathode materials in the future.

Composites of Graphene and LiFePO_4 as Cathode Materials for Lithium-Ion Battery:A Mini-review

This mini-review highlights selectively the recent research progress in the composites of Li Fe PO4 and graphene. In particularly, the different fabrication protocols, and the electrochemical performance of the composites are summarized in detail. The structural and morphology characters of graphene sheets that may affect the property of the composites are discussed briefly. The possible ongoing researches in area are speculated upon.