Electrochemical Performance of Nd1.95NiO4+δ Cathode supported Microtubular Solid Oxide Fuel Cells

Nd_1.95NiO_4+δ (NNO) cathode supported microtubular cells were fabricated and characterized. This material presents superior oxygen transport properties in comparison with other commonly used cathode materials. The supporting tubes were fabricated by cold isostatic pressing (CIP) using NNO powders and corn starch as pore former. The electrolyte (GDC, gadolinia doped ceria based) was deposited by wet powder spraying (WPS) on top of pre‐sintered tubes and then co‐sintered. Finally, a NiO/GDC suspension was dip‐coated and sintered as the anode. Optimization of the cell fabrication process is shown. Power densities at 750 °C of ∼40 mWcm⁻² at 0.5V were achieved. These results are the first electrochemical measurements reported using NNO cathode‐supported microtubular cells. Further developments of the fabrication process are needed for this type of cells in order to compete with the standard microtubular solid oxide fuel cells (SOFC).     

Synthesis and electrochemical performance of La0.6Ca0.4Fe1−xNixO3 (x = 0.1, 0.2, 0.3) material for solid oxide fuel cell cathode

Polycrystalline samples of La_0.6Ca_0.4Fe_1−xNi_xO₃ (x = 0.1, 0.2, 0.3) (LCFN) are prepared by liquid mix method. The structure of the polycrystalline powders is analyzed with X-ray powder diffraction data. The XRD patterns are indexed as the orthoferrite similar to that of LaFeO₃ having a single phase with orthorhombic perovskite structure (Pnma). The morphological characterization is performed by scanning electron microscopy (SEM) obtaining a mean particle size less than 300 nm.Polarization resistance is studied using two different electrolytes: Y-stabilized zirconia (YSZ) and Sm-doped ceria (SDC). Electrochemical impedance spectroscopy (EIS) measurements of LCFN/YSZ/LCFN and LCFN/SDC/LCFN test cells are carried out. These electrochemical experiments are performed at equilibrium from 850 °C to room temperature, under both zero dc current intensity and air. The best value of area specific resistance (ASR) obtained is 0.88 Ω cm², corresponding to the La_0.6Ca_0.4Fe_0.9Ni_0.1O₃ material using SDC as electrolyte. The dc four-probe measurement indicates that La_0.6Ca_0.4Fe_0.9Ni_0.1O₃ exhibits fairly high electrical conductivity, over 300 S cm⁻¹ at T > 500 °C.     

Cathode performance of LiMnPO4/C nanocomposites prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment

LiMnPO₄/C nanocomposites could be prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment in the range of spray pyrolysis temperature from 200 to 500 °C. The ordered LiMnPO₄ olivine structure without any impurity phase could be identified by X-ray diffraction analysis for all samples. It could be also confirmed from scanning electron microscopy and transmission electron microscopy observations that the final samples were the LiMnPO₄/C nanocomposites with approximately 100 nm in primary particles size. The LiMnPO₄/C nanocomposite samples were used as cathode active materials for lithium batteries, and the electrochemical tests were carried out for the cell Li|1 M LiPF₆ in EC:DMC = 1:1|LiMnPO₄/C at various charge/discharge rates in three charge modes. As a result, the final sample which was synthesized at 300 °C by spray pyrolysis showed the best electrochemical performance due to the largest specific surface area, the smallest primary particle size and a well distribution of carbon. At galvanostatic charge/discharge rates of 0.05 C, the cell delivered first discharge capacities of 123 and 165 mAh g⁻¹ in correspondence to charge cutoff voltages of 4.4 and 5.0 V, respectively. Furthermore, in a constant current-constant voltage charge mode at 4.4 V, the cells also exhibited initial discharge capacities of 147 mAh g⁻¹ at 0.05 C, 145 mAh g⁻¹ at 0.1 C, 123 mAh g⁻¹ at 1 C and 65 mAh g⁻¹ at 10 C. Moreover, the cells showed fair good cycleability over 100 cycles.     

Pulse electrodeposited cathode catalyst layers for PEM fuel cells

Nanostructured Pt and Pt₃Co cathodes for proton exchange membrane fuel cells (PEMFCs) have been prepared by pulse electrodeposition. For high utilization the catalyst nanoparticles are directly deposited on the microporous layer (MPL) of a commercial available gas diffusion layer (GDL). In order to increase the hydrophilic nature of the substrate surface and thus improve drastically the electrodeposition process and the fuel cell performance, prior to electrodeposition, the carbon substrate is submitted to O₂/Ar plasma activation. Cathodes with different amounts and distributions of Aquivion ionomer within the cathode catalyst layer (CCL) thickness (“homogeneous”, “gradient” and “anti-gradient”), different catalysts (Pt and Pt₃Co) at varied plasma duration and catalyst loading have been prepared. The cathodes are analysed via attenuated total reflection (ATR-IR), goniometer, SEM, 0.5 M H₂SO₄ half-cell and 25 cm² H₂/Air single PEMFC. The highest single fuel cell performance is obtained for 2 min plasma activated Pt₃Co cathode.     

In situ high-resolution transmission electron microscopy synthesis observation of nanostructured carbon coated LiFePO4

In situ high-resolution transmission electron microscopy (HRTEM) studies of the structural transformations that occur during the synthesis of carbon-coated LiFePO₄ (C-LiFePO₄) and heat treatment to elevated temperatures were conducted in two different electron microscopes. Both microscopes have sample holders that are capable of heating up to 1500 °C, with one working under high vacuum and the other capable of operating with the sample surrounded by a low gaseous environment. The C-LiFePO₄ samples were prepared using three different compositions of precursor materials with Fe(0), Fe(II) or Fe(III), a Li-containing salt and a polyethylene-block-poly(ethylene glycol)-50% ethylene oxide or lactose. The in situ TEM studies suggest that low-cost Fe(0) and a low-cost carbon-containing compound such as lactose are very attractive precursors for mass production of C-LiFePO₄, and that 700 °C is the optimum synthesis temperature. At temperatures higher than 800 °C, LiFePO₄ has a tendency to decompose. The same in situ measurements have been made on particles without carbon coat. The results show that the homogeneous deposit of the carbon deposit at 700 °C is the result of the annealing that cures the disorder of the surface layer of bare LiFePO₄. Electrochemical tests supported the conclusion that the C-LiFePO₄ derived from Fe(0) is the most attractive for mass production.     

Investigation of cobalt-free perovskite Ba0.95La0.05FeO3−δ as a cathode for proton-conducting solid oxide fuel cells

Cobalt-free perovskite Ba_0.95La_0.05FeO_3−δ (BLF) was synthesized. The conductivity of BLF was measured with a DC four-point technique. The thermal expansion coefficient of the BLF was measured using a dilatometer. The BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY7) electrolyte based proton conducting solid oxide fuel cells (SOFCs) were fabricated. A composite cathode with BLF + BZCY7 was used to mitigate the thermal expansion mismatch with the BZCY7 electrolyte. The polarization processes of the button cell NiO-BZCY7/BZCY7/BLF + BZCY7 were characterized using the complicated electrochemical impedance spectroscopy technique. The open circuit voltage of 0.982 V, 1.004 V, and 1.027 V was obtained at 700 °C, 650 °C, and 600 °C, respectively, while the peak power density of 325 mW cm⁻², 240 mW cm⁻², and 152 mW cm⁻², was achieved accordingly.     

Electrochemical properties of novel organodisulfide poly 1,2-bis(thiophen-3-ylmethyl)disulfane as cathode material for secondary lithium batteries

We successfully synthesized a new organodisulfide poly 1,2-bis(thiophen-3-ylmethyl)disulfane by a facile preparation method. The types of the chemical groups of poly-3-thienylthiophene were characterized by Fourier transform infrared spectroscopy (FTIR). The electrochemical properties of S–S bonds redox behavior in the organodisulfides were investigated in CH₃CN/0.1 M [Bu₄N] [PF₆] solution. The separation of the anodic and cathodic peak potentials for poly 1,2-bis(thiophen-3-ylmethyl)disulfane is 180 mV. The results indicated that poly 1,2-bis(thiophen-3-ylmethyl)disulfane has an excellent electrochemical reversibility. The average specific capacity of 230 mAh g⁻¹ for poly-3-thienylthiophene is about 2 times higher than that of LiCoO₂.     

微波炉用磁控管碳化钍钨阴极断裂失效分析

本文采用扫描电镜、X射线残余应力分析仪、金相显微镜等工具分析了微波炉用磁控管碳化钍钨阴极的断裂失效机理，碳化后钍钨阴极较粗大的晶粒与内应力是其断裂的主要原因。     

Microwave assisted synthesis and electrochemical behaviour of LiMg0.1Co0.9O2 for lithium rechargeable batteries

Layered LiMg_0.1Co_0.9O₂ has been synthesized using microwave assisted solution technique. The precursor has been subjected to thermo-gravimetric/differential thermal analysis (TG/DTA) and calcined at 850 °C. The precursor and the calcined powders were characterized by X-ray diffraction (XRD) to confirm the formation of single-phase layered material. Fourier transform infrared (FTIR) studies were carried out to understand the nature of the metal-ligand bond and the observations were consistent with the XRD spectrum. Scanning (SEM) and transmission electron microscope (TEM) images have been obtained to understand the surface morphology and the grain orientation of the synthesized material. Coin cells of 2016 type have been assembled using the synthesized layered material as the cathode active material, lithium foil as the counter and reference electrodes and 1 M LiPF₆ in 1:1 EC/DEC as the electrolyte. Coin cells were assembled and crimp sealed inside an argon filled glove box. The charge/discharge characteristics of the coin cells were evaluated galvanostatically in the potential range 2.7-4.3 V. Results indicate that LiMg_0.1Co_0.9O₂ delivers an average discharge capacity of ∼135 mAh g⁻¹ over the investigated 20 cycles and is a potential candidate for use as cathode material in lithium rechargeable cells.     

锂二次电池阴极材料—聚苯胺

本文介绍了作为锂二次电池阴极材料的聚苯胺的合成方法、结构,导电性和氧化还原可逆性。