Synthesis and characterization of porous monodisperse carbon spheres/selenium composite for high-performance rechargeable Li-Se batteries

In order to find the appropriate material to load selenium for higher performance of rechargeable Li-Se batteries, the resorcinol-formaldehyde resins derived monodisperse carbon spheres (RFCS)/Se composites were fabricated by the melting-diffusion method. The RFCS were obtained from initial carbonization of resorcinol-formaldehyde resins and subsequent KOH activation. Three kinds of samples of the RFCS/Se composites with different mass ratios were characterized by XRD, Raman spectroscopy, SEM, BET and EDS tests, which demonstrate that the samples with diverse mass fractions of selenium have distinct interior structure. The most suitable RFCS/Se composite is found to be the RFCS/Se-50 composite, which delivers a high reversible capacity of 643.9 mA·h/g after 100 cycles at current density of 0.2C.     

Development of composite LaNi0·6Fe0.4O3-δ-based air electrodes for solid oxide fuel cells with a thin-film bilayer electrolyte

In this study the bilayer composite electrodes based on LaNi₀.₆Fe₀.₄O_3-δ (LNF) electronic conductor and Bi₂O₃-based electrolytes doped with Er (Bi₁.₆Er₀.₄O₃, EDB) and Y (Bi₁.₅Y₀.₅O₃, YDB) have been developed and their performance has been investigated in the dependence on the electrolyte content and sintering conditions. The polarization resistance of the optimized electrodes with electrolyte content of 50 wt % in the functional layer and with the LNF-EDB-CuO collector is in a range of 0.65–1.09 Ω cm² at 600 °C and 0.10–0.12 Ω cm² at 700 °C. The polarization characteristics of the Bi-based electrodes are compared with those for the composite electrodes based on LNF and Ce_0.8Sm_0.2O_1.9 (SDC). The developed electrodes have been tested in a SOFC mode in the anode-supported cells with a thin film electrolyte of YSZ/YDC (Y-doped zirconia/ceria). The single cells with such cathodes are shown to have performance characteristics that are several times higher than that for the cell with a standard platinum cathode. This is due to the optimized content and dispersity of the components; high conductivity of ionic and electronic constituents of the composite electrodes; greatly extended triple phase boundary (TPB) of the electrochemical reaction and advanced electrode design with collector providing uniform current distribution.     

Fully Conjugated Phthalocyanine Copper Metal–Organic Frameworks for Sodium–Iodine Batteries with Long-Time-Cycling Durability

Rechargeable sodium–iodine (Na–I₂) batteries are attracting growing attention for grid-scale energy storage due to their abundant resources, low cost, environmental friendliness, high theoretical capacity (211 mAh g⁻¹), and excellent electrochemical reversibility. Nevertheless, the practical application of Na–I₂ batteries is severely hindered by their poor cycle stability owing to the serious dissolution of polyiodide in the electrolyte during charge/discharge processes. Herein, the atomic modulation of metal–bis(dihydroxy) species in a fully conjugated phthalocyanine copper metal–organic framework (MOF) for suppression of polyiodide dissolution toward long-time cycling Na–I₂ batteries is demonstrated. The Fe₂[(2,3,9,10,16,17,23,24-octahydroxy phthalocyaninato)Cu] MOF composited with I₂ (Fe₂–O₈–PcCu/I₂) serves as a cathode for a Na–I₂ battery exhibiting a stable specific capacity of 150 mAh g⁻¹ after 3200 cycles and outperforming the state-of-the-art cathodes for Na–I₂ batteries. Operando spectroelectrochemical and electrochemical kinetics analyses together with density functional theory calculations reveal that the square planar iron–bis(dihydroxy) (Fe–O₄) species in Fe₂–O₈–PcCu are responsible for the binding of polyiodide to restrain its dissolution into electrolyte. Besides the monovalent Na–I₂ batteries in organic electrolytes, the Fe₂–O₈–PcCu/I₂ cathode also operates stably in other metal–I₂ batteries like aqueous multivalent Zn–I₂ batteries. Thus, this work offers a new strategy for designing stable cathode materials toward high-performance metal–iodine batteries.     

Efficient strategy to boost the electrochemical performance of yttrium stabilized zirconia electrolyte solid oxide fuel cell for low-temperature applications

Yttrium stabilized zirconia (YSZ) used as the state-of-the-art electrolyte for solid oxide fuel cells (SOFCs) requires high temperature (over 800 °C) to realize sufficient oxygen ion conductivity. Thus, the high operational temperature is the main restriction for the commercial process of YSZ-based SOFCs. To obtain decent ionic conductivity at intermediate-low temperatures, Sr-free cathode LaNiO₃ is introduced into YSZ to construct a novel LaNiO₃-YSZ composite electrolyte, which is sandwiched by two Ni_0.8Co_0.15Al_0.05LiO_2-δ (NCAL) electrodes to assemble systematical fuel cells. This device presents an excellent peak output of 1045 mW cm^-2 at 600 °C and even 399 mW cm^-2 at 450 °C. A series of characterizations indicates that the oxygen ion conductivity of the LaNiO₃-YSZ composite is significantly promoted in comparison with that of pure YSZ, and the LaNiO₃ component has certain proton conductivity after hydrogenation. Both of the two factors contributes to the superior performance of such devices at intermediate-low temperatures. Furthermore, the sharp decrease in electronic conductivity for LaNiO₃ in hydrogen atmosphere combined with Schottky junction at the anode-electrolyte interface eliminates the short-circuiting problem. Our work demonstrates that incorporating Sr-free cathode LaNiO₃ into the YSZ electrolyte is an efficient strategy to boost the performance and reduce the operational temperature of YSZ-based SOFCs.     

Ultra-long cycle life and high rate performance subglobose Na3V2(PO4)2F3@C cathode and its regulation

A nitrogen-doped carbon coated subglobose Na₃V₂(PO₄)₂F₃@C (NVPF) cathode for sodium-ion batteries was synthesized by using hexadecyl trimethyl ammonium bromide (CTAB) as soft template and polyvinylidene fluoride (PVDF) as carbon source. CTAB plays a significant role on the formation of sphere micelles. Precursor ions are self-assembled on the surface at appropriate concentration and its mechanism is investigated in subglobose NVPF@C-4. CTAB also increases the conductivity of carbon layer as −(CH₃)₃N⁺ in CTAB is combined with residual carbon from PVDF to form partially N-doped carbon. Meanwhile, the carbon source PVDF contributes to prevent the generation of impurity Na₃V₂(PO₄)₃ by compensating the evaporative fluorine. Generally, CTAB and PVDF play multifunctional roles in regulating Na₃V₂(PO₄)₂F₃@C cathode with well-developed crystallite, high rate performance, good conductivity, and ultra-long cycle life. The specific capacity of NVPF@C-4 cathode at 0.1 C and 10 C is as high as 121.5 mAh·g⁻¹ and 99.2 mAh·g⁻¹ with high capacity retention of 90.1% even after 1000 cycles at 10 C. The excellent rate performance is also attributed to the high diffusion coefficient of Na⁺ and high exchange current according to the kinetic analysis. The enhanced electrochemical performances reveal the special regulation in this paper is feasible to obtain excellent structural stability of NVPF materials.     

Review on core-shell structured cathode for intermediate temperature solid oxide fuel cells

Lowing the operating temperature can greatly promote the commercialization of solid oxide fuel cells (SOFCs), however it also results in a significant increase in cell impedance, which is the bottleneck for the development of intermediate temperature SOFCs (IT-SOFCs). Major hurdles in developing conventional single-phase cathode materials for IT-SOFCs are poor electrochemical performance or durability. The investigation of new cathode materials or the optimization of the existing cathodes is imminent for the development of IT-SOFCs. Among them, core-shell structured cathode can combine the advantages of multiple components, and has been demonstrated with excellent oxygen reduction reaction (ORR) catalytic activity and long-term stability. This review summarizes the recent research progress on core-shell structured cathode for enhanced electrochemical performance, long-term stability, CO₂ tolerance and Cr tolerance. Furthermore, the future directions are discussed from a perspective of materials design, preparation and characterization. Core-shell structured cathodes are expected to play an increasingly critical role in the commercialization of IT-SOFCs.     

Exploration on sulfur/acid treatment of sepiolite composite positive electrode material for lithium-sulfur battery

High energy density battery system is endowed with more complex Lithium sulfur cathode whose electrochemical redox reaction and phase transition occurred due to multi electron participation. The different mole ratios of sepiolite mixed with sulfur were synthesized by acid cum thermal treatment method. The morphological analysis illustrates that the sepiolite powder is composed of micro fibrous bundles in the range of 1 μm to 10 μm. The sorption isotherms indicate that the sieved sepiolite (Sp) and different mole ratio (4, 6 and 8) of sepiolite/sulfur shows a type-IV isotherm of mesoporous material. The S/SvSp (sulfur/sieved sepiolite) composite cathode exhibits an initial discharge capacity of 1066 mAh g^?1 and attains a stable capacity of 596 mAh g^?1 during 40 cycles with 97% of efficiency. All the results correlated with the better electrochemical behaviour of electrode and it satisfies the needs of high energy density storage application.     

Plasma-assisted rapid sintering of nanotitania powders

In this work, Plasma-Assisted Rapid Sintering (PARS), a pulsed DC plasma system in a hollow cathode regime, is presented as a novel technology to sinter nanoceramics. Nano-TiO₂ powders are used as proof of concept and submitted to thermal treatment using several PARS conditions and sintering schedules. PARS heating process induced solely by the hollow cathode effect is consistent and affordable, providing a homogeneous temperature distribution to the compact. Furthermore, the heating rate and the maximum temperature are easily tunable by the discharge current applied in the plasma source and can go safely from room to maximum temperature in a matter of seconds with heating speed comparable with other reported rapid sintering techniques. Using 1-min of non-isothermal PARS cycles up to 1000 °C, porous nanostructured samples were obtained; reaching 80 % relative density while the grains remained at the nanoscale. Adding dwell times, the relative density was increased up to 96 % using a temperature plateau for up to 10 min, but the TiO₂ grains grow intensively when temperatures exceeded 1000 °C. The results indicate that the developed process is a promising new alternative technology for sintering nanoceramics.     

无机溶胶凝胶法制备铝酸盐对钡钨阴极性能的影响研究

针对高性能、长寿命空间行波管对阴极性能的苛刻需求,本文采用一种新型无机溶胶凝胶法制备钡钨阴极用铝酸盐,利用扫描电镜、X射线衍射仪分析铝酸盐的微观形貌、物相结构,并研究不同工艺路径制备铝酸盐对阴极发射性能、蒸发性能、寿命的影响。相比固相法制备的铝酸盐及阴极,无机溶胶凝胶法制备的铝酸盐烧结温度低、结晶性好、颗粒尺寸小(约1μm)且均匀性分散;无机溶胶凝胶法制备的阴极发射得到提高,发射拐点电流密度约为32.91 A/cm2,发射斜率约为1.403(1050℃(光亮温度));阴极蒸发速率较低,为2.5×10^-10 g/cm²·s(1050℃),同时阴极寿命提高了1.43倍。     

Carbon dioxide conversion to acetate and methane in a microbial electrosynthesis cell employing an electrically-conductive polymer cathode modified by nickel-based coatings

In this study, CO₂ conversion to acetate and CH₄ was achieved in a flow-through laboratory-scale microbial electrosynthesis (MES) cell composed of a 3D conductive polylactic acid (cPLA) lattice cathode with electrodeposited metal electrocatalyst coatings. The MES cell with a bare cPLA cathode showed the poorest performance with the lowest H₂ and CH₄ production rates and low Coulombic efficiency. This was ascribed to a poor electrocatalytic activity of cPLA towards H₂ production and high electrode resistivity. When the cPLA electrode was modified with metal coatings, the CH₄, acetate and H₂ production rate increased significantly, with the following trend: cPLA < Ni < NiFe < NiFeMn. The better performance of the metal-coated cPLA in terms of CH₄ production was attributed to the lower electrical resistance, enhanced H₂ production and enhanced electron transfer between the cathode and the biofilm. At the cell potential of 2.8 V, the best-performing NiFeMn cPLA cathode showed stable production of CH₄ (50 ± 6 mL d^?1), acetate (185 ± 27 mg d^?1), and H₂ (545 ± 175 mL d^?1) at close to 100% Coulombic efficiency.