Good Cycling Properties Research Articles

Peculiar martensitic microstructure and dislocation accumulation behavior in Ti-Ni-Cu shape memory alloys almost satisfying the triplet condition

Dislocation accumulation behavior at the lattice correspondence variant (CV) triplets of the Ti-Ni-Cu alloy close to the triplet condition (TC) was investigated by using in situ heating transmission electron microscopy observation. The martensitic microstructure of this alloy was peculiar because of no {011}o compound twin laminate as predicted by the phenomenological theory of martensite crystallography. The peculiar martensitic microstructure was composed of a combination of six different CVs connected by twin-relationship, including triplet and quadruple. Other types of triplets with higher incompatibility were not observed. It was revealed that few transformation-induced dislocations associated with thermal cycling were formed at the compatible martensitic microstructure satisfying the TC in the present alloy. The fact that few transformation-induced dislocations are formed in the TC microstructure in the Ti-30Ni-20Cu alloy during thermal cycling explains the good thermal cycling properties of this alloy.

Enhanced thermal performance of hybrid interface materials supported by 3D thermally conductive SiC framework

The rapid development of microelectronic integration technology is placing increasing demands on the safety performance of electronic devices. Excellent thermal interface materials (TIM) facilitate the dissipation of heat from electronic components, which ensures the safety of electronic equipment. In this work, a three-dimensional (3D) thermally conductive framework is constructed from carbon fibers to form silicon carbide (SiC) in situ. This is followed by vacuum impregnation with paraffin wax (PW) to produce phase change composites (PCCs). The results show that the SiC-based 3D thermally conductive framework has a hierarchical porous network structure, and the PCC indicates enhanced thermal conductivity and good anti-leakage properties. The thermal conductivity of PW @ CF1–Si1-1550 is 0.81 W K−1m−1, which is 4 times that of PW. In addition, the PCC also shows good thermal cycling properties, high thermal storage capacity (179.06 Jg-1), and good insulation properties. The PCC as described in this paper as TIM have considerable application potential in thermal management.

Synthesis of Al@Al2O3 microcapsules by a triple-coating method for high-temperature thermal energy storage

Metallic aluminum (Al) has a high melting point and high thermal storage density, making it a proper candidate for high-temperature thermal storage applications including waste heat recovery and solar thermal utilization. To solve the problems of easy leakage after melting, high reactivity and high corrosiveness during application, microcapsules with a stable alumina shell were developed based on a triple coating method. The preparation process was divided into three steps: (1) generation of a boehmite layer on the surface of the Al powders via boiling water treatment, which was designed to slow down the corrosion of the precursor in the subsequent treatment; (2) production of Al(OH)3 gel layer on the surface of the particles through Sol-gel treatment and (3) formation of the final dense Al2O3 shell after thermal oxidation treatment. The synthesized Al@Al2O3 microcapsules had a melting point of 655.5 °C and a latent heat of 227 J/g. Notably, the latent heat of microcapsules remained almost constant after 100 melting-solidification cycle experiments, indicating a good cycling properties. In summary, the newly developed Al@Al2O3 microcapsules have a broad application prospect in the field of high-temperature thermal storage.

Solid-state mechanochemical synthesis of Rh/Al2O3 catalysts for effective hydrolysis of ammonia borane

Aluminium oxide (Al2O3) is a promising catalyst support due to its excellent stability, high specific surface area, low price, and wide applicability. At present, most of the synthesis methods of Al2O3 are wet chemical process, and the solid-state synthesis of catalysts is underdeveloped under solvent-free conditions. In this study, we proposed a novel strategy for solvent-free synthesis of Rh/Al2O3 catalysts via mechanochemistry. The pore properties of the catalysts can be tuned by simply adjusting the amount of template CTAB and calcination temperatures. As a proof of concept, as-prepared catalysts are used to catalyze hydrolytic dehydrogenation of ammonia borane. The best catalyst Rh/Al2O3-CTAB(0.4)-500 achieves a total turnover frequency of 186.0 molH2·molRh−1·min−1 at 298 K and the activation energy is 44.8 kJ·mol−1. It also exhibits good cycling properties for catalyzing the hydrolysis of ammonia borane completely even after five runs. The catalysts were also characterized by various methods, including SEM, TEM, XPS, XRD, etc., to study the relationship between their structure and catalytic performance. The results show that the high activity of the catalyst is closely related to its large BET specific surface area and appropriate average pore size.

Study on the design and photocatalytic performance of TiO2@g–C3N4–Ag/Ag2O ternary heterojunction nanomaterials

In this work, we designed and prepared the TiO2@g–C3N4–Ag/Ag2O (TCNA) ternary nanoparticle materials in a simple and low-cost hydrothermal method, in which, small Ag/Ag2O nanoparticles were uniformly distributed on a layer of thin g-C3N4 nanosheets coated TiO2 nanospheres. By carefully changing the ratios of surface distributed Ag/Ag2O nanoparticles, the photocatalytic degradation performance of the prepared TCNA can be easily changed. Under the modified catalytic device, we found that a high degradation rate of about 99% at 90 min in degrading RhB can be obtained by TCNA-2 reached, which is 4.7 and 3.6 times higher than the photodegradation rate constants of pure TiO2 and TiO2@g-C3N4 composites, respectively. Furthermore, the prepared TCNA nanomaterials also showed high photocatalytic stability and good cycling properties. The scavengers study indicated that the ·O2− and ·OH were the main active groups of the obtained ternary photocatalysts. Subsequently, we proposed a suitable mechanism for exposing the high photocatalytic performance of our TCNA ternary nanomaterials, which may have a positive influence on the design and preparation of other high-performance ternary photocatalytic nanomaterials.

Engineering active sites on nitrogen-doped carbon nanotubes/cobaltosic oxide heterostructure embedded in biotemplate for high-performance supercapacitors

At present, both easy agglomeration of carbon nanotubes themselves and waste caused by chemical vapor deposition (CVD) have great pollution, which limits the use of carbon nanotubes (CNTs). A large number of hollow polyhedrons containing N-doped carbon nanotubes and Co3O4 nanoparticles (Co3O4 NPs) were well fabricated on a biotemplate by hydrothermal method, stirring method and pyrolysis process. The regular polyhedron was uniformly arranged on the external surface of diatomite with a natural porous structure, which aims to avoid the agglomeration of CNTs. The electrochemical testing result shows that the composite has promising electrochemical performance, which is embodied in a high specific capacity 894.6 F/g at 2 A/g, good rate performance and high cycling property. Finally, an assembled Co3O4 NP@CNTs@Diatomite//GR asymmetric supercapacitor has maximal energy density of 36.8 Wh/kg and maximal power density of 16,326.6 W/kg. Indeed, electrode design in this work provides an environmental synthesis idea for the decoration of CNTs on a certain substrate and displays an original electrode material based on diatomite.

Oxygen Vacancies‐rich Manganese Oxide with Flower‐like Nanosheets for High Performance Supercapacitors

AbstractHere, flower‐like manganese oxide with enriched oxygen vacancies were reported for high performance supercapacitors. The moderate oxygen‐vacancy were achieved by controlling annealing atmosphere. Benefiting from improving the conductivity and the density of active sites, MnOx−Ar sample as an electrode material has remarkable specific capacity (339 mAh g−1 at 0.5 A g−1), extraordinary rate capability (90 % capacity retention at 1 A g−1), and good cycling property (90 % capacity retention at 1 A g−1 after 5000 cycles). Additionally, the asymmetric supercapacitor (ASC) was assembled which used the MnOx−Ar sample as cathode and Kochen Black (KB) as anode, which displayed a remarkable energy density (16 Wh kg−1) at a large power density (7593 W kg−1). These results, on the one hand, further expand the application of MnO2‐based materials, and on the other hand, offer a new perspective for the oxygen non‐stoichiometry in material electrochemistry.

ZIF‐67 Derived Hollow Co9S8 as an Efficient Polysulfides Prohibitor for High Performance Lithium‐Sulfur Batteries

AbstractLithium‐sulfur batteries (LSBs) have received great attention due to their large energy density and specific capacity. Unfortunately, the poor cycle stability due to the shuttle effect of soluble polysulfides seriously impedes the application of LSBs. In order to solve this problem, we report the synthesis of ZIF‐67 derived hollow Co9S8 which is coated on the commercial separator for LSBs through a self‐template strategy. The hollow structure Co9S8 can capture a large amount of polysulfides during cycling, and the polar Co9S8 can chemically adsorb and catalyze the reaction intermediate, greatly reducing the migration of polysulfides. As a result, the hollow Co9S8 modified separator exhibits good rate performance and remains a capacity of 540.5 mAh g−1 after 500 cycles at 0.5 C as the sulfur area density of 3.0 mg cm−2. Even when the sulfur area density is increased to 5.0 mg cm−2, the battery using hollow Co9S8 modified separator still exhibits good cycle property.

Hierarchical design of core-shell structured Ni3S2/CoAl-LDH composites on rGO/Ni foam with enhanced electrochemical properties for asymmetric supercapacitor

Three-dimensional hierarchical hybrid composites incorporating both CoAl-layered double hydroxide and Ni3S2 grown onto the framework of reduced graphene oxide (rGO) on Ni foam were successfully fabricated by hydrothermal procedure combined with electrodeposition method (Ni3S2/CoAl-LDH/rGO). The Ni3S2 nanoplates was anchored on the surface of the CoAl-LDH/rGO nanosheets, forming a cross linked core-shell structure. Electrochemical measurements demonstrate that the outer Ni3S2 layer can significantly influence the morphology and electrochemical properties of the hybrid electrodes. Benefiting from its attractive structural feature and strong synergy of multiple components, excellent results were obtained in the composite with the optimal mass loading of Ni3S2 layer, which exhibited an excellent specific capacitance of 2457.5 F g−1 at 1 A g−1 and a desirable cycling behavior of 90.0% retention over 5000 cycles. The assembled asymmetric supercapacitor using Ni3S2/CoAl-LDH/rGO as positive electrode and active carbon as negative electrode delivers a high energy density of 59.8 W h kg−1 at a power density of 402.8 W kg−1 and a good cycling property (91% capacitance retention after 8000 cycles). These encouraging results demonstrate that such hybrid nanostructure provides great potential as electrode material for the energy storage devices.

Microwave-Assisted Synthesis of Tris-Anderson Polyoxometalates for Facile CO2 Cycloaddition.

Four new tris-Anderson polyoxometalates (POMs), (NH4)4[ZnMo6O18(C4H8NO3)(OH)3]·4H2O (1), (NH4)4[CuMo6O18(C4H8NO3)(OH)3]·4H2O (2), (TBA)3(NH4)[ZnMo6O17(C5H9O3)2(OH)]·10H2O (3) (TBA = n-C16H36N), and (NH4)4[CuMo6O18(C5H9O3)2]·16H2O (4), were synthesized by a microwave-assisted method. Single-crystal X-ray diffraction revealed that 1 and 2 contained a tris (trihydroxyl organic compounds) ligand grafted on one side, while two tris ligands were grafted on two sides to form χ/δ and δ/δ isomers in 3 and 4, respectively. 1H and 13C NMR spectra of the χ/δ isomer 3 were obtained for the first time, with six methylenes showing six peaks in the 1H NMR spectrum and only four peaks in the 13C NMR spectrum. Mass spectrometry monitoring revealed that during the microwave-assistant process the tris ligand can graft onto POMs to form 1, while tris directly coordinates with metallic heteroatoms to form isopolymolybdates during the conventional reflux synthesis process. In addition, 1-4 can catalyze CO2 with epoxides into cyclic carbonates with high selectivity and yields at an atmospheric pressure of CO2, which is lower than the pressure of CO2 in other catalysis using POMs as catalysts. Furthermore, 1-4 showed good catalytic stability and cycling properties. Mechanism studies substantiated POMs cocatalyzed with Br- to improve the catalytic yields.

An efficient method for large-scale preparation of high-purity α-Si3N4 nanowires and their electrochemical performance

An efficient and catalyst-free method for the large-scale preparation of high-purity α-Si3N4 nanowires was demonstrated by annealing absorbent cotton and silicic acid in a flowing nitrogen atmosphere. The pyrolysis of absorbent cotton generated a fluffy structure constructed by carbon microfibers, which could promote the growth of α-Si3N4 nanowires. The nanowires were characterized by XRD and XRD Rietveld refinement, SEM and TEM. The results indicated that the nanowires have diameters of 50–100 nm and lengths of tens to hundreds of microns. Vapor-solid (VS) mechanism was proposed to be responsible for the formation of nanowires. The α-Si3N4 nanowires were then applied as anode materials for lithium-ion batteries (LIBs), exhibiting good rate capability and cycling property.

High-capacity Li-excess lithium nickel manganese oxide as a Co-free positive electrode material

For the design of high-capacity and Co-free positive electrode material, stoichiometric LiNi1/2Mn1/2O2 and Li-excess Li1+x(NiyMn1-y)1-xO2 (0<x<1/3, y = 0.4 and 0.5) samples were prepared using coprecipitation–calcination. The basic LiNi1/2Mn1/2O2 structure is hexagonal layered rock-salt structure (R3¯m), but the sample has a biphasic composite of main Li-poor Li1-xTM1+xO2 (TM, transition metal) and minor Li-rich Li1+xTM1-xO2 phases after calcination below 950 °C. The fraction of the minor Li-rich phase decreased concomitantly with increasing calcination temperature. Only at 1000 °C was single-phase LiNi1/2Mn1/2O2 obtainable. The biphasic samples exhibited better electrochemical performance than that for the single-phase sample. Based on this result, two Li-excess Li1+x(NiyMn1-y)1-xO2 (0<x<1/3, y = 0.4 and 0.5) samples were synthesized by setting an excess amount of Li2CO3 (nominal Li/(Ni + Mn) ratio = 2) and calcination in air. Both samples were usefulness as a high-capacity positive electrode material exceeding 180 mA h g−1, with good cycling properties at 2.0–4.6 V.

Accommodation of a Large Amount of Lithium Ions in Silsesquioxane-pillared Carbon: A Potential Anode of an All-solid-state Lithium Ion Battery

More than 25 weight percent of lithium ions were accommodated in silsesquioxane-pillared carbon with very small interlayer expansion. It delivered reversible capacity of 1023 mAh/g with a relatively high first columbic efficiency of 67% and good cycling property as an anode of an all-solid-state lithium ion battery.

Electrochemical performance of polyacrylamide hydrogel based nitrogen-doped porous carbon for supercapacitor

Nitrogen-doped porous carbon materials for supercapacitor was successfully fabricated from precursor of polyacrylamide gel through freeze drying, carbonization and KOH activation process. The precursor of polyacrylamide gel was prepared using acrylamide and N,N-methylene diacrylamide as monomers and cross-linking agents, respectively. The nitrogen-doped porous carbon was tested by field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, Raman spectrum, X-ray electron spectrum and specific surface analysis, respectively. Further, the electrochemical performance of nitrogen-doped porous carbon was tested by using a three-electrode system, which exhibited large specific capacitance of 302.1 F/g at 1 A/g, good rate property (71.8%, 217 F/g at 20 A/g) and cycle property (96% after 8000 cycles). Symmetrical supercapacitor was also assembled with an extended operating voltage window of 1.8 V in 1 M Na2SO4 electrolyte. More significantly, the nitrogen-doped porous carbon maintains an energy density of 23.27 Wh/kg in the case of a power density of 450 W/kg.

CuFeS2 as an anode material with an enhanced electrochemical performance for lithium-ion batteries fabricated from natural ore chalcopyrite

Considering serious pollution from the traditional chemical synthesis process, the resource-rich, clean electrode materials are greatly desired. Conventional electrochemical performance improvement methods, such as quantum dot or coating, are complicated and costly. In this study, CuFeS2 with an enhanced cycle performance is prepared from natural ore chalcopyrite through simple flotation and acid leaching. We obtain micro-sized CuFeS2 with high yield and purity. Electrochemical measurement shows that the natural chalcopyrite with an EDD-S electrolyte displays a high initial charge capacity (992 mAh·g−1 at the initial discharge current density of 0.2 C), an excellent rate performance, and good cycle property. The discharge capacities are approximately 870, 850, 830, 800, 750, and 680 mAh·g−1 at current densities of 0.1, 0.2, 0.3, 0.5, 1, and 2 C, respectively. When the current density is reduced back to 0.1 C, the reversible capacity can recover to 860 mAh·g−1, the cyclability is impressive (initial capacity of 700 mAh·g−1 and 660 mAh·g−1 maintained for 1000 cycles at a high current density of 2 C, corresponding to an excellent capacity retention of 94% after 1000 cycles).

Plasticizer incorporated, novel eco-friendly bio-polymer based solid bio-membrane for electrochemical clean energy applications

High-molecular-weight, carbohydrate based Solid Biopolymer Electrolyte (SBE) pectin-lithium perchlorate [C6H10O7:LiClO4 = 60:40 molar mass percentage (m.m.%)] with ethylene carbonate (EC) as plasticizer has been prepared by simple solution casting technique. Addition of EC results in enhanced electrochemical window from 3.39 V to 3.55 V. The flexibility of the SBE is also improved which leads to attain an enriched ionic conductivity of 3.89 × 10−4 Scm−1 in the sample with optimum salt and plasticizer composition. The eco-friendly membrane with highest conductivity contributes good cycling properties and possesses higher value of cationic transference number when compared with other electrolyte samples. A lithium ion conducting battery constructed using the highly conducting polymer membrane sample is used to light up the red LED, display an Open Circuit Voltage (OCV) of 1.65 V.

Sol–gel synthesis of K1.33Mn8O16 nanorods and their applications for aqueous K-ion hybrid supercapacitors

K1.33Mn8O16 nanorods were successfully prepared by a facile sol–gel method with KHCO3, Mn(Ac)2 and citrate acid as raw materials. The cyclic voltammetry results demonstrate that the K1.33Mn8O16 nanorods exhibit a quasi-reversible K+ intercalation/deintercalation behavior in a 0.5 M K2SO4 aqueous solution. It has also been found that the assembled activated carbon (AC)//K1.33Mn8O16 asymmetric hybrid supercapacitor delivers an energy density of 17.74 Wh kg−1 at a power density of 210 W kg−1, and an energy density of 8.18 Wh kg−1 at a high power density of 2124 W kg−1. Moreover, the AC//K1.33Mn8O16 supercapacitor shows a good cycling property. To the best of our knowledge, the synthesis of K1.33Mn8O16 nanorods via the sol–gel route and the use of K1.33Mn8O16 in supercapacitors are reported for the first time.

Microstructure and Electrochemical Properties of ZnMn2O4 Nanopowder Synthesized Using Different Surfactants

ZnMn2O4 (ZMO) nanopowders have been synthesized by a hydrothermal method using different surfactants [cetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG)-400, and Polysorbate-80]. The as-prepared ZnMn2O4 samples exhibited single phase with tetragonal structure, showing honeycomb, spinel microsphere, and flower-cluster morphology, respectively. Cyclic voltammetry curves for all samples presented rectangular shape with symmetric nature and good cycling properties, with no obvious redox peak. Galvanostatic charge–discharge curves were triangular and symmetric. The specific capacitance of the ZnMn2O4 nanopowders gradually decreased with increase of the scanning rate. ZMO-PEG exhibited higher specific capacitance of 191 F g−1 at scan rate of 5 mV s−1 and retained superior large-current cycling stability of 98.4% after 1000 cycles compared with ZMO-CTAB (93.8%) or ZMO-Polysorbate-80 (97.7%). Electrochemical impedance spectroscopy revealed that the ZnMn2O4 nanopowders had low resistance. These results suggest that ZnMn2O4 nanopowders have good capacitance characteristics.

Dual-tuning the thermodynamics and kinetics: Magnesium-naphthalocyanine nanocomposite for low temperature hydrogen cycling

2,11,20,29-Tetra-tert-butyl-2,3-naphthalocyanine (TTBNc) was used as an alternative host to support magnesium (Mg) nanoparticles. After deposition and decomposition of dibutylmagnesium on TTBNc, Mg nanoparticles of around 4 nm supported on TTBNc were observed by TEM. These TTBNc stabilized Mg nanoparticles were found to absorb hydrogen at 100 °C and release hydrogen from 75 °C. The Mg-TTBNc material showed good hydrogen cycling properties and structural stability. Kinetic measurements showed fast hydrogen absorption within 2 min at 150 °C. The hydrogen desorption kinetics were slower at the same temperature but faster at 250 °C with 80% of the hydrogen desorbed within 1 h. Enthalpy and entropy for hydrogen uptake and release in Mg-TTBNc determined from PCT measurements were found to be of 52.7 ± 4.9 kJ mol−1 H2 and 107.8 ± 9.4 J K−1 mol−1 H2, respectively. These values are much lower than those of bulk Mg.

Superior performance of Na7V4(P2O7)4PO4 in sodium ion batteries.

A novel synthetic method has been investigated to fabricate a 1D nanostructure Na7V4(P2O7)4PO4. Mixed polyanion materials with a well-defined 3D framework channel can improve the electrochemical performance of sodium reversible insertion/extraction reactions, and can be especially beneficial for high rate performance and cycling capability. It approaches an initial reversible electrochemical capacity of 92.0 mA h g−1 with a high discharge potential over 3.85 V (vs. Na/Na+) and good cycling properties with a capacity retention of 81.4% after 300 cycles at a 0.5C rate in sodium systems. Taking into consideration the superior electrochemical characteristics, the phase-pure composite is considered to have a promising high rate capability as well as being a high capacity electrode material for advanced energy storage applications.