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For application in electric vehicles (EVs), the Li-air battery system needs an air intake system to supply dry oxygen at controlled concentration and feeding rate as the cathode active material. To facilitate the design of such air intake systems, we have investigated the effects of oxygen partial pressure (≤1 atm) on the performance of the Li-air cell, which has not been systematically examined. The amounts of consumed O 2 and evolved CO 2 from the Li-air cell are measured with a custom in situ differential electrochemical gas chromatography-mass spectrometry (DEGC-MS). The amounts of consumed O 2 suggest that the oxygen partial pressure does not affect the reaction mechanism during discharge, and the two-electron reaction occurs under all test conditions. On the other hand, the charging behavior varies by the oxygen partial pressure. The highest O 2 evolution ratio is attained under 70% O 2 , along with the lowest CO 2 evolution. The cell cycle life also peaks at 70% O 2 condition. Overall, an oxygen partial pressure of about 0.5–0.7 atm maximizes the Li-air cell capacity and stability at 1 atm condition. The findings here indicate that the appropriate oxygen partial pressure can be a key factor when developing practical Li-air battery systems. [ABSTRACT FROM AUTHOR]

The capacity limits, local formation of Li 2 O 2 , passivation of active surfaces, and depletion of oxygen by mass transport characteristics in a composite cathode are modeled, numerically simulated, and experimentally evaluated for non-aqueous Li-O 2 batteries employing composites of a solid polymer electrolyte and carbon particles as the cathode, Li metal as the anode, and an ion conductive oxide membrane as the separator. Although the theoretical maximum specific energy of the Li-O 2 battery is known to be 3458 Wh kg −1 cathode , our simulation predicts a maximum specific energy of 1840 Wh kg −1 cathode with an optimized weight ratio of all essential components as well as cathode thickness. A specific energy of 1713 Wh kg −1 cathode is experimentally demonstrated in a cell with a composite cathode of poly(ethylene oxide) electrolyte and Printex carbon nanoparticles with 48% carbon volume and 30 μm thickness. The model also predicts that the incorporation of voids in the cathode can significantly improve the specific energy. [ABSTRACT FROM AUTHOR]

New proton exchange membranes were prepared and evaluated as polymer electrolytes for a proton exchange membrane fuel cell (PEMFC). Two types of fluorinated poly(arylene ether)s (FPAEs) were synthesized by nucleophilic aromatic substitution of decafluorobiphenyl (DFBP) with 4,4′-(hexafluoroisopropylidene)diphenol (HFDP) and bisphenol-A (BPA). The FPAEs so prepared were converted into proton exchange polymers by sulfonation with fuming sulfuric acid (30% SO3). The FPAEs and sulfonated-fluorinated poly(arylene ether)s (S-FPAEs) with various sulfonation levels were characterized using 1H NMR, thermogravimetric analysis (TGA) and back titration, and then successfully evaluated as proton exchange membranes (PEM) with unit cell operation. power output measurements of S-DFBP-HFDP carried out at a cell temperature of 80 °C. They exhibited a maximum power density of 425.5 mW/cm2 at 1150 mA/cm2. [Copyright &y& Elsevier]

High-density sintered plate-type cathodes composed of only an active material can achieve a high energy density of lithium-ion batteries (LIBs) beyond the current state of the art. However, slow lithium ion movement in the solid-state cathode plate and deterioration of the grain boundary of sintered cathodes over many charge/discharge cycles are obstacles to commercialization. Herein, we present a new three-dimensional high-density sintered LiCoO 2 plate cathode with periodically aligned channels, which enable fast charging/discharging of high-energy-density LIBs. In addition, we investigate the grain-boundary cracking mechanism and introduce a conductive coating agent to LiCoO 2 cathodes that prevents crack propagation, enhances electron transfer between sintered LiCoO 2 grains, and prevents the formation of an undesirable cathode electrolyte interphase. In full-cell experiments, the cell with a sintered LiCoO 2 cathode with industrial-level current density (3.5 mA cm−2) has a volumetric capacity (723 mAh cm−3) 21% higher than that of a conventional cathode (597 mAh cm−3). The cathode coated with the conductive agent shows a 30% higher cycle life after testing for 500 cycles compared to the bare cathode. High-density sintered cathodes are fabricated with an industrially acceptable cycle lifetime of 84% capacity retention over 500 cycles at 1 C. [Display omitted] • A high-density 3D sintered-LiCoO 2 -plate cathode (HTS-LCO) was developed. • The conductive coating (C-PAI) prevented severe grain-boundary cracking in HTS-LCO. • HTS-LCO gave volumetric capacity 21% higher than that of a conventional cathode. • HTS-LCO exhibited good cycle stability at an industrial level current density. [ABSTRACT FROM AUTHOR]

Abstract: Organic–inorganic composite membranes for operation above 100°C in polymer electrolyte membrane fuel cells (PEMFCs) were prepared, characterized and cell-tested. Composite membranes were obtained by mixing organic polymers, which have a SO3H group as a proton conductor with inorganic material, SiO2, using the sol–gel process. Electron probe micro analyser (EPMA) was used to show the homogeneous and uniform distribution of SiO2. The physico-chemical properties of all membranes were investigated regarding their tensile strength, water uptake and thermogravimetric analyzer (TGA). Due to a higher water uptake and thermal stability of composite membranes, the cell performances at high temperatures above 100°C, were improved. In addition, the SiOH group in the composite membrane was shown to play a major role in capturing water strongly and maintaining proton conductivity even at high temperature. Furthermore, the fuel cell performance of organic–inorganic composite membranes was superior to that of the Nafion membrane at high current density over all ranges of temperature. [Copyright &y& Elsevier]

Sacrificial templating effect of mixed polymer matrix to create surface pores promoting the facile ion flow and close interaction of electrode and electrolyte. • Mixed polymer matrix provided a strong framework to restrict CNT migration. • Hot press proved to have enhance the performance with no structural deformation. • Easy access point for the electrolytes due to the emergence of surface pores. • Exhibited a specific energy of 814 Wh/kg -cell required for electric vehicles. Although Li-air batteries have been recognized as promising next-generation batteries for electric vehicles (EVs), there are still several issues in the development of practical cells that can achieve high specific energies for long driving ranges. In particular, it is important to employ a small amount of electrolyte and prevent it from escaping the cathode material during charging and discharging. Herein, a free-standing web-like mat cathode composed of mixed polymer nanofibers with high CNT loading is reported. High amounts of CNT (ca. 65.8 wt% of the polymer weight) is simultaneously loaded into the as-spun nanofibers with a mixed polymer matrix (consisting of polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP)). The domain occupied by PVP was converted into pores after a simple washing process, while the remaining PAN domain formed a backbone for the nanofibers. Using this cathode, a practical cell with a specific energy of 814 Wh/kg -cell is successfully developed by applying a controlled optimum ratio of electrolyte to CNT in the cathode. With these results, although still lacking, can provide handful insights and new directions towards development of future electrode materials as well as encourage to pursue strategies that requires minimal processing and activation steps while still achieving industrial acceptable performances. [ABSTRACT FROM AUTHOR]

Abstract A 500 mAh Li–Air battery is assembled using cell components and a structure that enable the construction of a high specific energy battery. Carbon nanotubes are used in the cathode so that the pore volume can be adjusted to reduce the amount of electrolyte while a high specific capacity of the cathode is maintained. Polymer ionic liquid is used in the electrolyte layer, and the weight of the cathode and electrolyte layer is 5.5 mg cm−2. The cell structure, which is prepared by folding a three-layer assembly of Li metal/electrolyte layer/cathode, reduces the weight contribution of the sealing and manifold materials. By folding the three-layer assembly ten times, a 500 mAh Li–Air battery with dimensions of 7 cm × 1 cm × 0.23 cm is prepared. The battery yields an areal capacity of 3.6 mAh cm−2 and a specific capacity of 4400 mAh g carbon −1, and the resulting specific energy and energy density are 1230 Wh kg−1 and 880 Wh L−1, respectively. The battery is able to cycle seven times at 500 Wh kg−1 before an abrupt decrease in its capacity is noted. Graphical abstract Image 1 Highlights • Design of Li–Air battery with specific energy over 1000 Wh kg−1 is presented. • Fold cell structure reduces weight of sealing and manifold materials. • A cell with dimension of 7 cm × 1 cm × 0.23 cm produces 500 mAh. • The battery could be cycled 7 times at the specific energy of 500 Wh kg−1. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting to its constituents, hydrogen and oxygen, is a promising approach to producing chemical fuels. The preparation of metal oxides on a conductive substrate with a well-defined structure has been an important issue for improving the efficiency of PEC water splitting. In this study, we have developed a facile synthetic process for the manufacture of WO 3 nanocrystals with full coverage on a fluorine-doped tin oxide (FTO) substrate. The preparation of WO 3 as a continuous film on the FTO substrate is indispensable to study charge separation processes in its composite structure. Typically, various ratios of WO 3 /BiVO 4 composite structures were prepared with the WO 3 held constant to investigate charge separation processes in WO 3 and BiVO 4 for efficient PEC water oxidation. The photocurrent initially drops and then rises with growing BiVO 4 molar ratios. We attribute this initial decrease in photocurrent to electron-hole recombination at the semiconductor-semiconductor interface. On the other hand, an improved photocurrent is attributed to enhanced charge separation of BiVO 4 on the WO 3 electrode. Our work reveals the important relationship between WO 3 and BiVO 4 in water oxidation reaction. [ABSTRACT FROM AUTHOR]

In this study, we made a novel alternative cathode material of molten carbonate fuel cell (MCFC) using electroless deposition of Co on the surface of the Ni powder. Using this manufacturing method, we expect that economical and large-scale cathode can be made easily. The cathode prepared by this method formed LiCo1−yNiyO2 phase in molten (Li0.62K0.38)2CO3 at 650 °C under CO2:O2=66.7:33.3% atmosphere, its solubility is 40% lower than that of NiO cathode. In the unit cell test, the performance of the cell composed of Co-coated Ni cathode was same as that of the cell composed of NiO cathode. Thus the cathode made by Co-coated Ni powder used as an alternative cathode can maintain the advantages of NiO cathode and lengthen the lifetime of MCFC. [Copyright &y& Elsevier]