•A smart control of perovskite is developed to obtain a high performance and stable catalyst.•The coupling of perovskite with Ag is helpful in advancing the catalytic activity.•The robustness and active sites have been systematically verified.Extensive research has been devoted to the development of advanced oxygen reduction reaction (ORR) catalysts with functionally diverse active sites. Herein, we show a smart approach to advancing the ORR catalytic activity of a 3D porous perovskite. The facile oxidative-reductive-oxidative (O-R-O) thermal treatment cycle executed on Ag doped LaFeO3 could stepwise switch on three different reaction sites (exsolved Ag-NPs, oxygen deficiency and Fe4+ with optimal electron configuration) for ORR. Detailed characterizations illustrate that the ORR activity is basically derived from the hierarchically porous scaffold which provides a large surface area and enough pore volumes for mass and ion diffusion. More importantly, the unique synergistic effects among three separate kinds of reaction sites endow the speed-up of oxygen adsorption, activation and O2− transportation. The exemplified results set out new design principles for the optimization of alternative catalysts.Herein, we show a smart approach to advancing the ORR catalytic activity of a 3D porous perovskite.Download high-res image (234KB)Download full-size image

•We report an efficient sulfur host based on two oxides, yielding high sulfur loading as high as 80 wt%.•The host could effectively trap lithium polysulfides benefitting from the unique structural and compositional advantages.•Lithium-sulfur batteries using this host exhibit excellent electrochemical performance.Although lithium-sulfur batteries show fascinating potential for high-capacity energy storage, their practical applications are hindered by the fast capacity decay and low sulfur utilization at high sulfur loading. Herein we report an efficient sulfur host based on two oxides, in which SiO2 hollow spheres with radial meso-channels are covered by a thin TiO2 coating. SiO2 spheres not only yield high sulfur loading as high as 80 wt% but also possess strong lithium polysulfides (LiPS) adsorption capability. The thin TiO2 coating can effectively prevent the LiPS outward diffusion, giving rise to a long-term stability. Meanwhile, the oxide-supported carbon from the carbonization of surfactants enables good electrical conductivity to facilitate electron access and improve sulfur utilization. Experimental and theoretical studies show the strong adsorption of LiPS by SiO2. Benefitting from the unique structural and compositional advantages, we achieve a high sulfur loading up to 80 wt% with ~65.5% and 33% capacity retentions over 500 and 1000 cycles when tested at 0.5 C and 1 C, respectively.Download high-res image (275KB)Download full-size image

In this paper, we report a unique approach to directly grow nano-scale cotton-like CuO in situ on a Cu current collector using a nano-second laser to ablate it, forming an excellent integrated electrode. This villous nano-cotton CuO is made of micro-scale cotton-like structures, which consist of a huge number of nano-scale particles around 5 nm in diameter. The CuO–Cu integrated anode prepared in 10 minutes by laser ablation exhibits excellent rate performance, coulombic efficiency and a long cycle life. After 800 cycles at 1.5 A g−1, the coulombic efficiency remains higher than 99% and the retention capacity reaches 393.6 mA h g−1. These, to our knowledge, are the highest achieved among currently available CuO integrated anodes. This unique performance is attributed to the villous cotton-like CuO structure, which effectively resists volume expansion and contraction, increases the adhesion of active materials to the current collector, and enhances the conduction of the anode. Laser ablation is a highly efficient and cost-effective approach to prepare integrated oxide-metal anodes for LIBs with a long cycle life. In addition, FexOy–Fe, NixOy–Ni integrated anodes were also prepared for LIBs to verify the wide applicability of this method.

A double-shell hollow structured MnO2@TiO2 anode material has been successfully synthesized through a two-step template method. The monodispersed carbon spheres synthesized through a hydrothermal method act as the templates. The inner part of the carbon template acts as a sacrificial template to form the void and the outer part of it plays the role of self-template to synthesize hollow MnO2 spheres. The composition, crystallinity, morphology, and valence state of the final product MnO2@TiO2 are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The electrochemical performances of the double-shell hollow structured MnO2@TiO2 anode material have been comprehensively improved. The specific capacity of the composite retains 802 mA h g−1 at the current rate of 200 mA g−1 after 200 cycles, and it can still retain about 400 mA h g−1 at a higher current rate of 1 A g−1. Finally, a more detailed charging/discharging process of MnO2 is proposed.

While lithium metal anodes have the highest theoretical capacity for rechargeable batteries, they are plagued by the growth of lithium dendrites, side reactions, and a moving contact interface with the electrolyte during cycling. Here, we synthesize a non-porous, elastomeric solid–electrolyte separator, which not only blocks dendritic growth more effectively than traditional polyolefin separators at large current densities, but also accommodates the large volume change of lithium metal by elastic deformation and conformal interfacial motion. Specially designed transparent capillary cells were assembled to observe the dynamics of the lithium/rubber interface in situ. Further experiments in coin cells at a current density of 10 mA cm−2 and an areal capacity of 10 mA h cm−2 show improved cycling stability with this new rubber separator.

Porous acicular mullite (3Al2O3·2SiO2) ceramics containing Cu3Mo2O9 as a soot oxidation catalyst was fabricated by a novel approach using commercial powders of Al2O3 and CuO, and powder obtained by controlled oxidation of ground waste MoSi2. The obtained material consisted of elongated mullite grains which are known to be effective in carbon soot removal from diesel engine exhaust. The presence of in situ created Cu3Mo2O9 was found to catalyze the carbon burnout which is an extremely important feature when it comes to filter regeneration, i.e., the captured soot removal. The carbon burnout temperature in the sample containing 12 wt% CuO was by 90 °C lower than that in the sample without CuO. Effect of sintering temperature as well as the effect of amount of CuO additive on mullite properties were studied. It was found that the increase in amount of CuO in samples sintered at 1300 °C decreased porosity and increased compressive strength of the porous mullite ceramics. The addition of 12 wt% CuO increased the strength of the porous mullite ceramics up to 70 MPa, whereas the porosity was reduced from 62% in the mullite without CuO to 44% in the mullite ceramics containing 12 wt% CuO. Although affected by the amount of CuO, the microstructure still consisted of elongated mullite grains.

Herein, we designed an extremely facile method to prepare well-defined MnO2@CeO2–MnO2 ball-in-ball binary oxide hollow spheres by employing carbon spheres (CSs) as sacrificial templates. The synthesis process involves a novel self-assembled approach to prepare core–shell CSs@CeO2 precursor, which would directly react with KMnO4 aqueous solution to form yolk–shell CSs@MnO2/CeO2–MnO2 precursor in the following step. Well-dispersed Ce–Mn binary oxide with double-shelled hollow sphere structure could be achieved after annealing the precursor in air. The evolution process and formation mechanism of this novel structure were thoroughly studied in this paper. Especially the as-prepared double-shell MnO2/CeO2–MnO2 hollow spheres exhibited enhanced catalytic activity for CO oxidation compared with the pure MnO2 hollow spheres and pure CeO2 hollow spheres. We believe the high surface area, hierarchical porous structures, and strong synergistic interaction between CeO2 and MnO2 contribute to the excellent catalytic activity. Most importantly, this method could be extended to prepare other transition metal oxides. As an example, triple-shelled Co–Mn composite hollow spheres assembled by ultrathin nanoplates were successfully prepared.Keywords: catalytic oxidation; CeO2; double-shell; hollow spheres; MnO2

A solid Li-ion conductor with a high room temperature Li-ion conductivity and small interfacial resistance is required for its application in next-generation Li-ion batteries. Here, we prepared a cubic perovskite-related oxide with the general formula Li3/8Sr7/16Hf1/4Ta3/4O3 (LSHT) by a conventional solid-state reaction method, which was studied by X-ray diffraction, electrochemical impedance spectroscopy, and 7Li MAS NMR. Li3/8Sr7/16Hf1/4Ta3/4O3 has a high Li-ion conductivity of 3.8 × 10–4 S cm–1 at 25 °C and a low activation energy of 0.36 eV in the temperature range 298–430 K. It exhibits both high stability and small interfacial resistance with commercial organic liquid electrolytes, which makes it promising as a separator in Li-ion batteries.

Herein, SiO2@CeO2 composite microspheres were successfully prepared via a hydrothermal assisted layer-by-layer self-assembly method employing colloid SiO2 as the template, which was fabricated by a typical Stöber method. Monodispersed CeO2 hollow spheres with a narrow size distribution were achieved after etching colloid SiO2 templates through NaOH. The resultant samples were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscopy (TEM), Fourier translation infrared spectroscopy (FT-IR), X-ray photoelectron spectrum (XPS), and Nitrogen adsorption–desorption isothermal. Specifically, the shell thickness and the mesoporous structure of the hollow sphere can be easily controlled by changing the concentration of cerium source.

Micro-honeycomb barium titanate (BaTiO3) ceramics, which have uniformly distributed one-dimensional pore channels, were prepared by freeze-casting suspensions of hydrothermally synthesized BaTiO3 nanopowder with a particle size of 100 nm. The effects of sintering schedules such as sintering temperature and holding time on pore size distribution, porosity, pore wall density and grain size were studied. The grain size on the pore wall of BaTiO3 is around 1–2 μm after two-step sintering. The crystallographic structure of all samples was tetragonal phase regardless of the sintering schedules. Ferroelectric domains were shaped in a stripe and the domain width obviously increased after polarization. The micro-honeycomb BaTiO3 sintered at lower temperature or shorter holding time showed larger piezoelectric coefficient d33 and smaller dielectric constant εr.

MnO2 nanomaterials are synthesized via calcinations in air at various temperatures. Amorphous MnO2 masses appear between 100 and 300 °C and nanorods form above 400 °C. Transmission and scanning electron microscopy are used to observe the geometries of each material, with further structural analyses conducted using X-ray photoelectron spectroscopy, X-ray diffraction, and BET method. The electrochemical properties are investigated through galvanostatic charge/discharge cycling, electrochemical impedance spectra, and cyclic voltammetry within a three-electrode test cell filled with 1 mol L−1 Na2SO4 solution. The slightly asymmetric galvanostatic cycling curves suggest that the reversibility of the Faradaic reactions are imperfect, requiring a larger time to charge than discharge. The specific capacitances of each sample are calculated and trends are identified, proving that the samples synthesized at higher temperatures exhibit poorer electrochemical behaviors. The highest calculated specific capacitance is 175 F g−1 by the sample calcinated at 400 °C. However, the lower temperature samples exhibit more favorable geometric properties and higher overall average specific capacitances. For future research, it is suggested that surface modifications such as a carbon coating could be used in conjunction with the MnO2 nanorods to reach the electrochemical properties required by contemporary industrial applications.

•Composite design disentangles thinness-strength dilemma in garnet.•Simple and efficient mechanical strength and gas impermeability test method.•Electrical property of the composite electrolyte verified in a Li–H2O2 cell.Li-ion ceramic electrolyte material is considered the key for advanced lithium metal batteries, and garnet-type oxides are promising ceramic electrolyte materials. To disentangle the thinness-strength dilemma in garnet-type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) electrolyte, we designed and successfully synthesized a ceramic–ceramic composite electrolyte, i.e. a honeycomb-Al2O3 pellet supported LLZTO membrane. The honeycomb-Al2O3 pellet acts as a supporter to the thin LLZTO membrane and makes the whole composite electrolyte strong enough, while the straight holes in the Al2O3 supporter can be filled with liquid electrolyte and acts as channels for Li+ transportation. Such a composite design eliminates the concern over the LLZTO membrane's fragility, and keeps its good electrical property.

•We prepare porous mullite/Na2SO4 composites by infiltration method.•The porous mullite possesses unidirectionally aligned open pores.•The composites possess improved heat storage properties.•Increasing porosity and infiltration time will increase the infiltration ratio.•Decreasing pore size and infiltration temperature will increase the infiltration ratio.The porous mullite/Na2SO4 composites with both novel structure and improved heat storage properties were successfully prepared by infiltration of the molten Na2SO4 into the porous mullite matrix, which was fabricated by TBA-based freezing casting method. The effects of fabrication parameters on pore structure of the porous mullite matrix, the infiltration ratio of molten Na2SO4 and heat storage properties of the composites were investigated extensively. The results show that the infiltration ratio of the molten Na2SO4 decreases with decreasing the porosity and increasing the infiltration temperature and the average pore size of the porous mullite matrix. While it increases initially with increases of the infiltration time, and tends to remain constant thereafter. The optimal infiltration temperature and infiltration time are 950 °C and 1 h, respectively. The unidirectionally aligned open pores in the porous mullite matrix benefit the infiltration process, and the higher infiltration ratio of the molten Na2SO4 and the relatively larger specific heat capacity of the mullite powders both contribute to the higher heat storage density of the composites.

Well-dispersed CeO2–CuOx composite hollow spheres have been successfully synthesized through a facile reflux method using carbon spheres as sacrificial templates. The shells of the hollow spheres, ∼40 nm in thickness, consist of self-assembled 10–15 nm sized nanoparticles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to study the structural features of the CeO2–CuOx composite hollow spheres. X-ray photoelectron spectroscopy (XPS) confirmed that most of the copper element is distributed on the surface of the CeO2 shell support. The CeO2–CuOx composite hollow spheres exhibited enhanced catalytic activity for CO oxidation: complete CO conversion could be obtained at 112 °C. The excellent catalytic activity could be ascribed to the hollow structure, high specific surface area and the strong synergistic interaction between CeO2 and CuOx.

•Li+/H+ exchange led to a new garnet oxide “Li6.5 − xHxLa3Zr1.5Ta0.5O12”.•The exchanged protons in H-LLZT displaced Li from the octahedral sites.•The Li ions in H-LLZT become less mobile.•The occupancy of Li on the octahedral sites (especially 48g sites) was reduced.•The amorphous phase LiAlO2 in the grain boundary dissolved on exposure to water.The Li-ion conductor “Li6.5La3Zr1.5Ta0.5O12” (LLZT) with garnet structure is prepared by solid-state reaction in an alumina crucible; its stability in water is investigated at room temperature. A Li+/H+ exchange is characterized by TGA, 7Li and 27Al MAS NMR, neutron diffraction, and TEM. In water, Li+/H+ exchange leads to a new garnet oxide “Li6.5 − xHxLa3Zr1.5Ta0.5O12” (H-LLZT) with space group Ia–3d; the lattice parameter of H-LLZT is increased by the exchanged protons. Both LLZT and a grain boundary phase LiAlO2 are unstable in water. The exchanged protons in H-LLZT displace Li from the octahedral sites bridging the 24d tetrahedral sites; they form a strong OH bond that distorted the site. The amorphous phase LiAlO2 in the grain boundary dissolves on exposure to water, which inhibits Li-ion transport across the grain boundary.

•Homemade LLZTO sheet was compared with commercial LTAP sheet.•Novel double-electrolyte and mechanical–rechargeable Li–H2O2 semi-fuel cell.•Two Li–H2O2 semi-fuel cells were assembled using LLZTO and LTAP sheet.•The LLZTO-based cell has lower internal resistance and better cell performance.An Al2O3-doped Li6.4La3Zr1.4Ta0.6O12 (LLZTO) cylinder with a cubic garnet structure was prepared by solid state reaction and pressureless sintering. The LLZTO cylinder showed a high relative density of ~ 94%. LLZTO sheets (200 μm in thickness) were obtained by slicing the LLZTO cylinder using a low speed diamond saw. Ionic conductivity of the sheet was as high as 1.02 × 10− 3 S·cm− 1 at room temperature. Two specially designed Li–H2O2 semi-fuel cells were assembled using the LLZTO sheet and LTAP sheet (from Ohara, Japan), respectively. The semi-fuel cell employing the LLZTO sheet showed a lower internal resistance and a much higher maximum power density. It discharged at a constant current of 1.0 mA for 1500 min (two “mechanical recharge–discharge” cycles), and relative flat discharge voltage plateaus of ~ 2.5 V were observed, with an average lithium metal utilization in the cell of 82.0%. The LLZTO thin sheets showed that high quality and could improve the performance of the Li–H2O2 semi-fuel cell.

A specially designed Li–H2O2 semi-fuel cell based on hybrid electrolytes is proposed. It is a combination of fuel cell and lithium battery. Five “mechanical charge–discharge” cycles (800 hours in total) of the Li–H2O2 semi-fuel cell were conducted. The cell exhibits fast mechanical rechargeability, good stability and high lithium utilization. Output power of the Li–H2O2 semi-fuel cell can be flexibly adjusted by changing H2O2 concentration.

Electrophoretic deposition of montmorillonite modified by acrylamide monomers was performed in an aqueous suspension. The acrylamide monomers functioned as both the intercalating agent and the reacting monomers. The suspension was prepared by the dispersion of organic clay in distilled water, and followed by the electrophoretic deposition. After that, the deposit on the electrode was treated by ultraviolet-radiation free-radical polymerization with benzil as a photo-initiator. The films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electronic microscopy (SEM) and nano-indentation. The d-spacing of (0 0 1) diffraction peak of the clay was increased from 1.29 nm to 1.89 nm by the intercalation of acrylamide. The SEM showed a layered structure similar to those found in the natural nacre. The hardness and modulus of the film are 0.95 GPa and 16.92 GPa, respectively.

•We prepare porous mullite/Na2SO4 composites by infiltration method.•The porous mullite possesses unidirectionally aligned open pores.•The composites possess improved heat storage properties.•Increasing porosity and infiltration time will increase the infiltration ratio.•Decreasing pore size and infiltration temperature will increase the infiltration ratio.The porous mullite/Na2SO4 composites with both novel structure and improved heat storage properties were successfully prepared by infiltration of the molten Na2SO4 into the porous mullite matrix, which was fabricated by TBA-based freezing casting method. The effects of fabrication parameters on pore structure of the porous mullite matrix, the infiltration ratio of molten Na2SO4 and heat storage properties of the composites were investigated extensively. The results show that the infiltration ratio of the molten Na2SO4 decreases with decreasing the porosity and increasing the infiltration temperature and the average pore size of the porous mullite matrix. While it increases initially with increases of the infiltration time, and tends to remain constant thereafter. The optimal infiltration temperature and infiltration time are 950 °C and 1 h, respectively. The unidirectionally aligned open pores in the porous mullite matrix benefit the infiltration process, and the higher infiltration ratio of the molten Na2SO4 and the relatively larger specific heat capacity of the mullite powders both contribute to the higher heat storage density of the composites.

•Perovskite-type Li3/8Sr7/16Hf1/4Ta3/4O3 (LSHT) with high density was prepared by solid–state reaction.•The total Li–ion conductivity of LSHT with 2 wt% LiF at 25 °C is 3.3 × 10−4 S cm−1.•The activation energy is about 0.36 eV in the temperature range 298–450 K.•LSHT with 2 wt% LiF has a small interfacial resistance with organic electrolyte.•A Li/LiFePO4 battery with LSHT–2 wt% LiF has a good cycling performance.Cubic perovskite–type oxide Li3/8Sr7/16Hf1/4Ta3/4O3 (LSHT) is a promising solid electrolyte material for next–generation Li–ion batteries such as all–solid–state Li batteries and Li–redox flow batteries due to its high room–temperature Li–ion conductivity and good chemical compatibility with commercial organic liquid electrolyte. High relative density is another important requirement for these applications. Here we investigate the influence of sintering additives (Li3BO3, Li4SiO4, LiF) on the density, the total Li–ion conductivity, the interfacial conductivity against commercial liquid electrolyte, and the cycling performance of the hybrid Li-ion cells. The results show that comparing with other additives, LSHT sintered with 2 wt% LiF shows the highest Li–ion conductivity (3.3 × 10−4 S cm−1) and the smallest interfacial resistance (125 Ω cm2) against organic electrolyte at room temperature; Li/LiFePO4 batteries with LSHT pellets fired with 2 wt% LiF have the best cyclability and the highest coulombic efficiency (99.6 ± 0.04%) in 50 cycles.

While lithium metal anodes have the highest theoretical capacity for rechargeable batteries, they are plagued by the growth of lithium dendrites, side reactions, and a moving contact interface with the electrolyte during cycling. Here, we synthesize a non-porous, elastomeric solid–electrolyte separator, which not only blocks dendritic growth more effectively than traditional polyolefin separators at large current densities, but also accommodates the large volume change of lithium metal by elastic deformation and conformal interfacial motion. Specially designed transparent capillary cells were assembled to observe the dynamics of the lithium/rubber interface in situ. Further experiments in coin cells at a current density of 10 mA cm−2 and an areal capacity of 10 mA h cm−2 show improved cycling stability with this new rubber separator.