Button cells based on the Li/Bi2O3 couple

Lithium button cells (1.5 V) with thermally treated Bi₂O₃ cathodes (additive free), mainly of 11.4 × 3.4 mm standard size (100 mA h), have been constructed. They are characterized by high volumetric energy densities even at high discharge rates. The cell behaviour is also satisfactory after 1 year's storage, at low temperature (?10 °C), and under 500 μA pulses. Comparison with analogous Li cells (Li/FeS₂ and Li/Pb₂Bi₂O₅) or aqueous cells (Zn/HgO and Zn/Ag₂O) confirms the usefulness of this system as a power source for microelectronic devices. This was also substantiated by field tests.     

Performance and durability of an anode-supported solid oxide fuel cell with a PdO/ZrO2 engineered (La0.8Sr0.2)0.95MnO3-δ-(Y2O3)0.08(ZrO2)0.92 composite cathode

PdO/ZrO₂ co-infiltrated (La_0.8Sr_0.2)_0.95MnO_3-δ-(Y₂O₃)_0.08(ZrO₂)_0.92 (LSM-YSZ) composite cathode (PdO/ZrO₂+LSM-YSZ), which adsorbs more oxygen than equal amount of PdO/ZrO₂ and LSM-YSZ, is developed and used in Ni-YSZ anode-supported cells with YSZ electrolyte. The cells are investigated firstly at temperatures between 650 and 750 °C with H₂ as the fuel and air as the oxidant and then polarized at 750 °C under 400 mA cm^?2 for up to 235 h. The initial peak power density of the cell is in the range of 438–1207 mW cm^?2 at temperatures from 650 to 750 °C, corresponding to polarization resistance from 1.04 to 0.35 Ω cm². This result demonstrates a significant performance improvement over the cells with other kinds of LSM based cathode. The cell voltage at 750 °C under 400 mA cm^?2 decreases from initial 0.951 to 0.89 V after 170 h of current polarization and remains essentially stable to the end of current polarization. It is identified that the self-limited growth of PdO particles is responsible for the cell voltage decrease by reducing the length of triple phase boundary affecting the high frequency steps involved in oxygen reduction reaction in the cathode.     

Low temperature studies on rechargeable lithium cells

Rechargeable lithium cells using intercalating cathodes of TiS₂, a-MoS₃, and mixed a-MoS₃TiS₂ were studied at temperatures from 25 °C to ?40 °C. On the basis of conductivity investigations, LiAsF₆ and LiAlCl₄ electrolytes were selected for use in a binary solvent containing 24.4 mass % 4-butyrol actone in 1,2-dimethoxyethane. The Li/TiS₂ and Li/a-MoS₃TiS2 cells cycled well at 2 mA cm^?2 down to ?30 °C, but at 5 mA cm^?2 at these very low temperatures, cell capacities were significantly lower. At room temperatures all cells performed slightly better in 1 mol dm^?3 LiAsF₆ than in 0.8 mol dm^?3 LiAlCl₄ in 24 mass % 4-BL/DME. However, at temperatures below ?10 °C the latter electrolyte was found to be superior.     

The investigation of Ag & LaCo0.6Ni0.4O3−δ composites as cathode contact material for intermediate temperature solid oxide fuel cells

The high interface resistance between cathodes and interconnects is a major cause for performance degradation of solid oxide fuel cells (SOFCs). Ag particles were mixed to LaCo_0.6Ni_0.4O_3?δ (LCN) matrix which prevented the silver densification and demonstrated porosity microstructure. The composites with different Ag content were evaluated as cathode contact materials with SUS430 alloy as interconnects. The area specific resistance (ASR) of SUS430/10%Ag & LCN/SUS430 showed the optimal performance in which the ASR was 73 mΩ cm² after 50 h at 750 °C and showed stable property in 10 thermal cycles from 200 °C to 750 °C. The excellent performance of 10%Ag & LCN is attributed to the high conductivity of silver, the stable microstructure of LCN and its good interface adhesion with the interconnect alloy. With 10%Ag & LCN as cathode contact materials, the power density of a single cell reached 0.623 W/cm² at 750 °C and the average degradation is lower than 1% in 3 thermal cycles.     

Intriguing electrochemistry in low-temperature single layer ceramic fuel cells based on CuFe2O4

A composite of CuFe₂O₄ and Gd-Sm co-doped CeO₂ is studied for a single layer ceramic fuel cell application. In order to optimize the cell performance, the effects of sintering temperatures (600 °C, 700 °C, 800 °C, 900 °C and 1000 °C) were investigated for the fabrication of the cells. It was found that the cells sintered at 700 °C outperformed other cells with a maximum peak power density of 344 mW/cm² at 550 °C. The electrochemical impedance spectroscopy analysis on the best cell revealed significant ohmic losses (0.399 Ω cm²) and polarization losses (0.174 Ω cm²) in the cell. The HR-TEM and SEM gave microstructural information of the cell. The HT-XRD spectra showed the crystal structures in different sintering temperatures. The cell performance was stable and the composite material did not degrade during an 8 h stability test under open-circuit condition. This study opens up new avenues for the exploration of this nanocomposite material for the low temperature single component ceramic fuel cell research.     

The lithium—sulfur dioxide primary battery — its characteristics,performance and applications

The lithium—sulfur dioxide battery is a new primary battery system with many advantages over conventional batteries. It has an energy density up to 330 W h/kg (150 W h/lb.), two to four times greater than zinc batteries, and can perform to temperatures as low as ?54 °C (?65 °F). The battery can withstand high temperature storage 71 °C (160 °F) for long periods of time and its shelf life is projected to be 5 – 10 years at 21 °C (70 °F). The chemistry, construction and detailed performance characteristics of the battery are presented. The Li/SO₂ system provides an all-purpose, all-climate primary battery that is capable of filling a wide variety of military, industrial and consumer applications. A number of these applications are discussed. With increasing production and cost reduction, the Li/SO₂ battery will be cost-competitive and will receive wide acceptability and use.     

In-situ Ni exsolution from NiTiO3 as potential anode for solid oxide fuel cells

Sample NiTiO₃ (NTO) is prepared by the molten salts synthesis route as a potential anode material for solid oxide fuel cell (SOFC) applications. An additional sample impregnated with 5 mol%Ni (N-NTO) is also presented. Structural characterization reveal a pure NiTiO₃ phase upon calcination at 850 °C and 1000 °C. Redox characterization by temperature programmed reduction tests indicate the transition from NiTiO₃ to Ni/TiO₂ at ca. 700 °C. Ni nanoparticles (ca. 26 nm) are exsolved in-situ from the structure after a reducing treatment at 850 °C. Catalytic activity tests for partial oxidation of methane performed in a fixed bed reactor reveal excellent values of activity and selectivity due to the highly dispersed Ni nanoparticles in the support surface. Time-on-stream behavior during 100 h operation in reaction conditions for sample N-NTO yield a stable CH₄ conversion. Electrolyte supported symmetrical cells are prepared with both materials achieving excellent polarization resistance of 0.023 Ω cm² in 7%H₂/N₂ atmosphere at 750 °C with sample N-NTO. The maximum power density achieved is of 273 mW cm⁻² at 800 °C with a commercial Pt ink used as a reference cathode, indicating further improvement of the system can be achieved and positioning the N-NTO material as a promising SOFC anode material.     

Multilayer tape casting of large-scale anode-supported thin-film electrolyte solid oxide fuel cells

Tape casting is conventionally used to prepare individual, relatively thick components (i.e., the anode or electrolyte supporting layer) for solid oxide fuel cells (SOFCs). In this research, a multilayer ceramic structure is prepared by sequentially tape casting ceramic slurries of different compositions onto a Mylar carrier followed by co-sintering at 1400 °C. The resulting half-cells contains a 300 μm thick NiO–yttria-stabilized zirconia (YSZ) anode support, a 20 μm NiO–YSZ anode functional layer, and an 8 μm YSZ electrolyte membrane. Complete SOFCs are obtained after applying a Gd_0.1Ce_0.9O₂ (GDC) barrier layer and a Sm_0.5Sr_0.5CoO₃ (SSC) -GDC cathode by using a wet-slurry spray method. The 50 mm × 50 mm SOFCs produce peak power densities of 337, 554, 772, and 923 mW/cm² at 600, 650, 700, and 750 °C, respectively, on hydrogen fuel. A short stack including four 100 mm × 150 mm cells is assembled and tested. Each stack repeat unit (one cell and one interconnect) generates around 28.5 W of electrical power at a 300 mA/cm² current density and 700 °C.     

Experimental investigation of CO tolerance in high temperature PEM fuel cells

In the present work, the effect of operating a high temperature proton exchange membrane fuel cell (HT-PEMFC) with different reactant gases has been investigated throughout performance tests. Also, the effects of temperature on the performance of a HT-PEMFC were analyzed at varying temperatures, ranging from 140 °C to 200 °C. Increasing the operating temperature of the cell increases the performance of the HT-PEMFC. The optimum operating temperature was determined to be 160 °C due to the deformations occurring in the cell components at high working temperatures. To investigate the effects of CO on the performance of HT-PEMFC, the CO concentration ranged from 1 to 5 vol %. The current density at 0.6 V decreases from 0.33 A/cm² for H₂ to 0.31 A/cm² for H₂ containing 1 vol % CO, to 0.29 A/cm² for 3 vol % CO, and 0.25 A/cm² for 5 vol % CO, respectively. The experimental results show that the presence of 25 vol % CO₂ or N₂ has only a dilution effect and therefore, there is a minor impact on the HT-PEMFC performance. However, the addition of CO to H₂/N₂ or H₂/CO₂ mixtures increased the performance loss. After long-term performance test for 500 h, the observed voltage drop at constant current density was obtained as ～14.8% for H₂/CO₂/CO (75/22/3) mixture. The overall results suggest that the anode side gas mixture with up to 5 vol % CO can be supplied to the HT-PEMFC stack directly from the reformer.     

Electrochemistry of a nonaqueous lithium/sulfur cell

The development and the electrochemistry of low-rate laboratory prototype Li/S button cells is described. The cell consists of a lithium anode, a porous catalytic current collector which is loaded with sulfur, and an organic solvent containing lithium polysulfide. The case of the cell was made from stainless steel and sealing was accomplished by the use of a combination of organic elastomer and cement (with no crimp). After 3 weeks storage at 60 °C, the button cells lost only about 1 mg of weight. The lithium polysulfide reacts with the Li anode to form a passivating layer which acts as a solid electrolyte interphase (SEI). The e.m.f. of the cells changes from 2.38 to 2.15 V depending on the composition of the solutions. Cells exhibit flat discharge curves at low drains. The energy density of the cells is 730 W h/kg or 900 W h/l at room temperature and 950 W h/kg or 1200 W h/l at 60 °C (calculated on the basis of all cell components, excluding the case). Storage and discharge tests at 60 °C show a capacity loss of 2 – 5% per month depending on solution composition. This indicates a shelf life of at least 10 years at room temperature.     

PVDF-HFP/PET/PVDF-HFP composite membrane for lithium-ion power batteries

In this study, a novel polymer electrolyte composite membrane is successfully fabricated using electrospinning and solution casting. The composite membrane comprises two microporous poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) layers plus an intermediate quaternary ammonium-containing SiO₂ nanoparticles modified polyethylene terephthalate (PET) nanofibrous nonwoven to form a sandwiched PVDF-HFP/PET/PVDF-HFP composite, which is employed as a separator for lithium-ion batteries (LIBs). The properties of the PET composite membrane are compared with those of commercial PE separator, such as the morphologies, physical properties, and electrochemical performances. According to our results, the composite membrane demonstrates superior thermal stability (thermal shrinkage ～8%), electrolyte-philicity (contact angle ～2.9°), electrolyte uptake and retention (282%, 74%), and ionic conductivity (～10^?3 S cm^?1). The separators are assembled into Li/LiFePO₄ cells for electrochemical tests, showing that the PET composite membrane cells exhibit higher capacities than those with the PE separator at 0.2–10C both at 25 °C and 55 °C. The discharge capacity retention and coulombic efficiency of the PET composite membrane cells at 1C/1C for 200 cycles can be respectively enhanced about 20% and 2% at 55 °C as compared to the PE separator cells. These results demonstrate that our prepared PET composite membrane is highly promising for LIB applications.     

Synthesis features of barium titanate in the field of concentrated light energy

It is shown that barium titanate can be synthesized, if a concentrated light flux with a density of 100 W/cm² acts to a TiO₂ + BaCO₃ mixture. Samples sintered at T = 1350°C from grinded melt are characterized by higher mechanical strength and permittivity with respect to barium titanates manufactured according to ceramic technologies.     

Planar proton-conducting ceramic cells for hydrogen extraction: Mechanical properties,electrochemical performance and up-scaling

Proton-conducting ceramics, which selectively separate H₂ from any hydrogen-containing gas could play a role in the future of the growing hydrogen market. In recent years, membrane technologies related to H₂ extraction became attractive solutions to produce pressurized high-purity hydrogen. Yttrium-doped barium zirconate/cerate materials (BaCe_xZr_1-x-yY_yO_3-δ) are among the most studied and used materials. In this study, symmetrical cells consisting of a protonic electrolyte (BaCe_0·2Zr_0·7Y_0·1O_3-δ (BCZY27), 10–15 μm in thickness) surrounded by two cermet electrodes (BCZY27–Ni (50?50 vol%), 150 μm) were prepared for H₂ extraction applications. The cells were prepared via tape-casting and co-sintered at 1575 °C. The cells were up-scaled to an area of 135 cm². The fracture toughness of the cermet electrodes was determined to be 2.07 (±0.05) MPa · m^1/2 at room temperature using the double torsion technique. Impedance spectra were recorded on the symmetrical cells between 650 and 800 °C in 3% humidified 50% H₂/50% N₂ atmosphere and at 650 °C varying the hydrogen partial pressure (20% < pH₂<100%). In 50% H₂/50% N₂ with 3% H₂O the cells demonstrated an ohmic resistance of 0.59 and 0.44 Ω cm,² an average electrode polarization resistance of 0.10 and 0.09 Ω cm² (per one electrode) at 650 and 800 °C, respectively. Moreover, a stability test was performed over 400 h highlighting the stable electrochemical properties of the symmetrical membranes.     

Li/SOCl2 cells for high temperature applications

The capacity of Li/SOCl₂ cells operating at temperatures as high as 150 °C has been measured at discharge rates up to 5 mA/cm². The results indicate the unique chemical and electrochemical stability of the system, manifested by its ability to be discharged continuously at 150 °C for more than 2 months while obtaining 70% of the cell nominal capacity.The capacity-temperature plot shows a maximum at 50 °C. Above 50 °C the capacity decreases as a result of the increase in the self-discharge current at higher temperature. An anomalous capacity increase is found at temperatures above 100 °C. Above this temperature it has been shown that thermal decomposition products may increase the cathodic reaction rate and modify the structure of the passivation layer on the anode surface. Over the 100 – 150 °C temperature range the lithium chloride film morphology, as analysed by SEM, tends to be of a smaller crystal size the higher the temperature. This trend is in opposition to that found at the lower temperature range, e.g., ?40 to 70 °C. In addition, the decomposition product, e.g., SO₂, improves the transport properties of the electrolyte and thus increases the carbon cathode efficiency.     

Electrochemical performance and stability of nano-structured Co/PdO-co-impregnated Y2O3 stabilized ZrO2 cathode for intermediate temperature solid oxide fuel cells

Palladium (Pd) is an attractive cathode catalyst component for solid oxide fuel cells (SOFCs) that has high tendency to agglomerate during operation at around 800 °C. This work shows that such agglomeration can be inhibited by alloying Co into Pd. PdO, Pd_0.95Co_0.05O, Pd_0.90Co_0.10O, and Pd_0.80Co_0.20O were synthesized and characterized. Powder X-ray diffraction patterns at 750 and 900 °C confirmed that PdO decomposition to Pd which normally occurred at 840 °C was suppressed for Co containing Pd alloys while thermal gravimetric analyses indicated improved redox reversibility of PdO ? Pd conversion for alloys during the thermal cycling between 600 and 900 °C. Scanning electron microscopy images supported these arguments. Pd_0.90Co_0.10+yttria stabilized zirconia (YSZ) electrode (i.e., 10 mol % Co containing PdO-impregnated YSZ electrode) displayed the highest oxygen reduction reaction (ORR) performance and stability. The polarization resistance for ORR on Pd_0.90Co_0.10+YSZ cathode is only 0.088 Ω cm² at 750 °C. During polarization test at 750 °C, Pd_0.90Co_0.10+YSZ cathode showed stable performance for 30 h while the performance of Pd+YSZ cathode degraded after 10 h.     

Characteristics of La0.8Sr0.2Ga0.8Mg0.2O3-δ-supported micro-tubular solid oxide fuel cells with LaCo0.4Ni0.6-xCuxO3-δ cathodes

In this study, micro-tubular solid oxide fuel cells (T-SOFCs) with extruded La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM) electrolyte as the mechanical support and LaCo_0.4Ni_0.6O_3-δ (LCNO) or LaCo_0.4Ni_0.4Cu_0.2O_3-δ (LCNCO) as cathodes were prepared and characterized. Partial substitution of Cu for the Ni-ion positions in the LCNO lattices was found to significantly enhance the densification and accelerate the grain growth. The porosity-corrected electrical conductivity was significantly increased from 1275 S/cm for LCNO ceramic to 1537 S/cm for LCNCO ceramic, because the acceptor doping was compensated by the formation of hole carriers that produced additional polarons and significantly augmented the electrical conductivity. SOFCs with three configurations were built in this study, including Cell A that had a lanthanum-doped ceria (LDC) buffer layer inserted between the LSGM electrolyte and the LCNCO cathode, Cell B that used an LCNO-LSGM composite cathode, and Cell C that featured an LCNCO-LSGM composite cathode. Among the three cells, Cell C with 263 μm of LSGM electrolyte possessed the lowest Ohmic resistance of 0.89 Ω cm², a polarization resistance of 0.69 Ω cm², and the highest maximum power density of 178 mW cm^?2 at 750 °C.     

Electrochemical performances of LiNiCoMn bifunctional electrode for low temperature solid oxide fuel cells

Lithium transition metal oxides LiNi_0.83Co_0.11Mn_0.06O₂ (NCM-83) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM-811) are prepared and acted as cathodes and bifunctional electrodes for low temperature solid oxide fuel cells with H₂ and CH₄ fuels. The Ni anode-supported cell with NCM-83 cathode exhibits maximum power density (P_max) of 0.72 W cm⁻² with H₂ fuel at 600 °C. The symmetric cell with NCM-83 electrodes shows high P_max of 0.465 W cm⁻² with H₂ fuel and 0.354 W cm⁻² with CH₄ fuel at 600 °C. And the P_max of the cell with NCM-811 as anode and NCM-83 as cathode is 0.204W cm⁻² with H₂ fuel at 600 °C. The oxygen vacancies in NCM materials are conducive to the rapid oxygen ion conduction of the cathode, and in the anodic reduction atmosphere, the NCM materials will generate Ni/Co active particles in situ, proving the NCM materials can be advanced bifunctional electrode materials for hydrogen oxidation reaction and oxygen reduction reaction at low temperature.     

High-performance solid oxide fuel cells with fiber-based cathodes for low-temperature operation

Low-temperature operation of solid oxide fuel cells (SOFCs) results in deterioration in electrochemical performance due to sluggish oxygen reduction reaction (ORR) at the cathode. To enhance the reaction pathway for ORR, La_0.8Sr_0.2MnO₃ (LSM) nanofibers were fabricated by electrospinning and used for low-temperature solid oxide fuel cells operated at 600–700 °C. The morphological and structural characteristics show that the electrospun LSM nanofiber has a highly crystallized perovskite structure with a uniform elemental distribution. The average diameter of the LSM nanofiber after sintering is 380 nm. A symmetric cell of nanofiber-based LSM cathode on scandia-stabilized zirconia (SSZ) electrolyte pellet exhibits much lower area specific resistances compared to commercial LSM powder-based cathode. A single cell based on the nanofiber LSM cathode on yttrium-doped barium cerate-zirconia (BCZY) electrolyte exhibits a power density of 0.35 Wcm⁻² at 600 °C, which increases to 0.85 Wcm⁻² at 700 °C. The cell has an area specific resistance (ASR) of 0.46 Ωcm² at 600 °C, which decreases to 0.07 Ωcm² at 700 °C. The results indicate that the LSM electrode fabricated by the electrospinning process produces a nanostructured porous electrode which optimizes the microstructure and significantly enhances the ORR at the cathode of SOFCs.     

Synergistic effect of TiF3@ graphene on the hydrogen storage properties of Mg–Al alloy

Mg–Al alloy was prepared by sintering and mechanical alloying, and the effects of graphene (Gp), TiF₃ and Gp/titanium (III) fluoride (TiF₃) on the hydrogen storage properties of the Mg–Al alloy were studied. The results show that Gp and TiF₃ could improve the hydrogen storage properties of Mg–Al alloy. In particular, Gp and TiF₃ showed good synergistic effect for enhancing the hydrogen storage properties of Mg–Al alloy. For example, when 1.0 wt% of H₂ was absorbed/desorbed, the hydrogen adsorption/desorption temperature of the Mg–Al alloy and Mg–Al-M (M = Gp, TiF₃, and TiF₃@Gp) composites were 241/343 °C, 185/310 °C, 229/292 °C and 159/280 °C, respectively. For the Mg–Al alloy, the apparent activation energy was 176.5 kJ mol^?1, and it decreased to 139.8 kJ mol^?1, 171.6 kJ mol^?1, and 94.3 kJ mol^?1, with the addition of Gp, TiF₃ and TiF₃@Gp composites, respectively. Evidently, the comprehensive hydrogen storage properties of Mg–Al alloy were improved remarkably under the synergistic effect of Gp and TiF₃.     

Response surface optimization of syngas production from greenhouse gases via DRM over high performance Ni–W catalyst

The process parameters for dry reforming of methane (DRM) over Ni–W/Al₂O₃–MgO catalyst are optimized using response surface methodology (RSM). The Ni–W bimetallic catalyst is synthesized by co-precipitation method followed by impregnation. The catalysts are characterized by BET, XRD, FESEM, EDX and TEM; to study physicochemical properties, morphology, composition, crystallite size and deposited carbon. The effect of process parameters, i.e., reaction temperature (600^oC–800 °C) and feed gas ratio (0.5–1.5) on the CH₄, CO₂ conversions and syngas ratio are studied. A temperature of 777.29 °C with CH₄: CO₂ of 1.11 at GHSV of 36,000 cm³gm.cat^?1h^?1, delivered the CH₄ and CO₂ conversions of 87.6% and 93.3%, respectively along with H₂:CO of 1. The predicted process parameters were verified through actual experimental analysis at the optimized conditions, and results agreed with CCD of the RSM model with insignificant error. The MWCNT formed during DRM avoided catalyst deactivation and delivered stable performance over 12 h of reaction test at the optimized conditions.