Hierarchical porous three-dimensional MnCo2O4 nanowire bundles were obtained by a universal and low-cost hydrothermal method, which subsequently act as a carbon-free and binder-free cathode for Li—O2 cell applications. This system showed a high discharge capacity of up to 12 919 mAh g–1 at 0.1 mA cm–2 and excellent rate capability. Under constrained specific capacities of 500 and 1000 mAh g–1, Li—O2 batteries could be successfully operated for over 300 and 144 cycles, respectively. Moreover, their charge voltage was markedly decreased to about 3.5 V. Their excellent electrochemical performance is proposed to be related to the conductivity enhancements resulting from the hierarchical interconnected mesoporous/macroporous weblike structure of the hybrid MnCo2O4 cathode, which facilitated the electron and mass transport. More importantly, after 2 months of cycling, the microstructure of the cathode was maintained and a recyclability of over 200 cycles of the reassembled Li—O2 cells was achieved. The effects of the level of electrolyte and corrosion of the lithium anode during long-term cycling on the electrochemical property of Li—O2 cells have been explored. Furthermore, the nucleation process of the discharge product morphology has been investigated.Keywords: binder-free; carbon-free; free-standing catalysts; lithium-oxygen batteries; MnCo2O4 nanowires;

•3D Si/CNCs with a hollow nanostructure was synthesized by W/O emulsion technique.•The 3D Si/CNCs can effectively solve the volume expansion problem.•Si/CNCs exhibit a high capacity of 1226 mAh g−1 at 0.5 A g−1 over 100 cycles.•An excellent rate capability of 547 mAh g−1 can be attained at 10 A g−1.Carbon nanotubes have attracted widespread attention as ideal materials for Lithium-ion batteries (LIBs) due to their excellent conductivity, mechanical flexibility, chemical stability and extremely large surface area. Here, three-dimensional (3D) silicon/carbon nanotube capsule composites (Si/CNCs) are firstly prepared via water-in-oil (W/O) emulsion technique with more than 75 wt% loading amount of silicon. CNCs with unique hollow sphere structure act as a 3D interconnected conductive network skeleton, and the cross-linked carbon nanotubes (CNTs) of CNCs can effectively enhance the strength, flexibility and conductivity of the electrode. This Si/CNCs can not only alleviate the volume expansion, but also effectively improve the electrochemical performance of the LIBs. Such Si/CNCs electrode with the unique structure achieves a high initial discharge specific capacity of 2950 mAh g−1 and retains 1226 mAh g−1 after 100 cycles at 0.5 A g−1, as well as outstanding rate performance of 547 mAh g−1 at 10 A g−1.

•Novel Co-free Cu1.4Mn1.6O4 spinel cathode are prepared and evaluated for IT-SOFCs.•CMO shows good thermal and chemical compatibility with ScSZ electrolyte material.•CMO exhibits a low polarization resistance of 0.143 Ω cm2 at 800 °C.•A remarkable power output of 1076 mW cm−2 is achieved at 800 °C.In this work Cu1.4Mn1.6O4 (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu+/Cu2+ and Mn3+/Mn4+ couples exist in the CMO sample, and a maximum conductivity of 78 S cm−1 is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc2O3 stabilized ZrO2 (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm2 at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm−2 at 800 °C under H2 (3% H2O) as the fuel and ambient air as the oxidant. These results indicate that Cu1.4Mn1.6O4 is a superior and promising cathode material for IT-SOFCs.A novel cobalt-free Cu1.4Mn1.6O4 (CMO) spinel oxide was synthesized and assessed as a potential SOFC cathode. Low polarization resistances for CMO were 0.143 and 0.317 Ω cm2 at 800 and 750 °C, respectively. Furthermore, a remarkable power output of 1076 mW cm−2 is achieved at 800 °C by a Ni-ScSZ anode supported ScSZ electrolyte single cell with the CMO cathode.

•Carbon fiber cloth (CFC) is applied as interlayer between the separator and cathode.•The interlayer helps to anchor the dissolved active material during cycling.•A high-rate, long-life Li-S battery with high sulfur loading has been designed.Significant efforts have been made to eliminate the shuttle effect created by the surface modification of separator or by adding interlayers. However, much of the research so far requires elaborate and costly material processing steps that did not necessarily result in substantially improved cell performances. In this contribution, a three-dimensional carbon fiber cloth (CFC) is placed between the separator and the sulfur cathode to accommodate and capture the soluble polysulfide intermediates. The cells with this interlayer show an initial discharge capacity of 6.89 mAh cm−2, which remains substantial after 100 cycles at 1C (6.69 mAh cm−2). CFC interlayers provide an efficient and cost effective route for developing promising lithium-sulfur batteries with long cycle stability and good rate capability.A three-dimensional carbon fiber cloth (CFC) is placed between the separator and the sulfur cathode to accommodate and capture the soluble polysulfide intermediates. The cells with this interlayer show an initial discharge capacity of 6.89 mAh cm−2, which remains substantial after 100 cycles at 1C (6.69 mAh cm−2).

•Sr2Fe1.5Mo0.4Nb0.1O6−δ –Sm0.2Ce0.8O2−δ composite cathodes are prepared by a one-pot method.•SFMNb-40SDC cathode exhibits the lowest Rp of 0.047°Ωcm2 at 800 °C.•Single cell with SFMNb-40SDC cathode shows a maximum power density of 1.22 W cm−2 at 800 °C.In this paper, Sr2Fe1.5Mo0.4Nb0.1O6−δ (SFMNb)−xSm0.2Ce0.8O2−δ (SDC) (x = 0, 20, 30, 40, 50 wt%) composite cathode materials were synthesized by a one-pot combustion method to improve the electrochemical performance of SFMNb cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The fabrication of composite cathodes by adding SDC to SFMNb is conducive to providing extended electrochemical reaction zones for oxygen reduction reactions (ORR). X-ray diffraction (XRD) demonstrates that SFMNb is chemically compatible with SDC electrolytes at temperature up to 1100 °C. Scanning electron microscope (SEM) indicates that the SFMNb-SDC composite cathodes have a porous network nanostructure as well as the single phase SFMNb. The conductivity and thermal expansion coefficient of the composite cathodes decrease with the increased content of SDC, while the electrochemical impedance spectra (EIS) exhibits that SFMNb-40SDC composite cathode has optimal electrochemical performance with low polarization resistance (Rp) on the La0.9Sr0.1Ga0.8Mg0.2O3 electrolyte. The Rp of the SFMNb-40SDC composite cathode is about 0.047 Ω cm2 at 800 °C in air. A single cell with SFMNb-40SDC cathode also displays favorable discharge performance, whose maximum power density is 1.22 W cm−2 at 800 °C. All results indicate that SFMNb-40SDC composite material is a promising cathode candidate for IT-SOFCs.

In this work NiO/3 mol% Y2O3–ZrO2 (3YSZ) and NiO/8 mol% Y2O3–ZrO2 (8YSZ) hollow fibers were prepared by phase-inversion. The effect of different kinds of YSZ (3YSZ and 8YSZ) on the porosity, electrical conductivity, shrinkage and flexural strength of the hollow fibers were systematically evaluated. When compared with Ni–8YSZ the porosity and shrinkage of Ni–3YSZ hollow fibers increases while the electrical conductivity decreases, while at the same time also exhibiting enhanced flexural strength. Single cells with Ni–3YSZ and Ni–8YSZ hollow fibers as the supported anode were successfully fabricated showing maximum power densities of 0.53 and 0.67 W cm−2 at 800 °C, respectively. Furthermore, in order to improve the cell performance, a Ni–8YSZ anode functional layer was added between the electrolyte and Ni–YSZ hollow fiber. Here enhanced peak power densities of 0.79 and 0.73 W cm−2 were achieved at 800 °C for single cells with Ni–3YSZ and Ni–8YSZ hollow fibers, respectively.

•Three-dimensional ordered mesoporous CuCo2O4 materials as catalysts in lithium-oxygen batteries were prepared.•They show high bifunctional activity for oxygen reduction and evolution reactions.•They especially improve the reversibility and cycling stability of Li–O2 batteries.Three-dimensional ordered mesoporous (3DOM) CuCo2O4 materials have been synthesized via a hard template and used as bifunctional electrocatalysts for rechargeable Li-O2 batteries. The characterization of the catalyst by X-ray diffractometry and transmission electron microscopy confirms the formation of a single-phase, 3-dimensional, ordered mesoporous CuCo2O4 structure. The as-prepared CuCo2O4 nanoparticles possess a high specific surface area of 97.1 m2 g− 1 and a spinel crystalline structure. Cyclic voltammetry demonstrates that mesoporous CuCo2O4 catalyst enhances the kinetics for either oxygen reduction reaction (ORR) or oxygen evolution reaction (OER). The Li-O2 battery utilizing 3DOM CuCo2O4 shows a higher specific capacity of 7456 mAh g− 1 than that with pure Ketjen black (KB). Moreover, the CuCo2O4-based electrode enables much enhanced cyclability with a 610 mV smaller discharge–recharge voltage gap than that of the carbon-only cathode at a current rate of 100 mA g− 1. Such excellent catalytic performance of CuCo2O4 could be associated with its larger surface area and 3D ordered mesoporous structure. The excellent electrochemical performances coupled with its facile and cost-effective way will render the 3D mesoporous CuCo2O4 nanostructures as attractive electrode materials for promising application in Li-O2 batteries.

A three-dimensional (3D) graphene–Co3O4 electrode was prepared by a two-step method in which graphene was initially deposited on a Ni foam with Co3O4 then grown on the resulting graphene structure. Cross-linked Co3O4 nanosheets with an open pore structure were fully and vertically distributed throughout the graphene skeleton. The free-standing and binder-free monolithic electrode was used directly as a cathode in a Li–O2 battery. This composite structure exhibited enhanced performance with a specific capacity of 2453 mA h g−1 at 0.1 mA cm−2 and 62 stable cycles with 583 mA h g−1 (1000 mA h gcarbon−1). The excellent electrochemical performance is associated with the unique architecture and superior catalytic activity of the 3D electrode.

The electrochemical performance of one-dimensional porous La0.5Sr0.5CoO2.91 nanotubes as a cathode catalyst for rechargeable nonaqueous lithium-oxygen (Li-O2) batteries is reported here for the first time. In this study, one-dimensional porous La0.5Sr0.5CoO2.91 nanotubes were prepared by a simple and efficient electrospinning technique. These materials displayed an initial discharge capacity of 7205 mAh g−1 with a plateau at around 2.66 V at a current density of 100 mA g−1. It was found that the La0.5Sr0.5CoO2.91 nanotubes promoted both oxygen reduction and oxygen evolution reactions in alkaline media and a nonaqueous electrolyte, thereby improving the energy and coulombic efficiency of the Li-O2 batteries. The cyclability was maintained for 85 cycles without any sharp decay under a limited discharge depth of 1000 mAh g−1, suggesting that such a bifunctional electrocatalyst is a promising candidate for the oxygen electrode in Li-O2 batteries.

•Three-dimensional ordered mesoporous ZnCo2O4 materials as catalysts in lithium-oxygen batteries were prepared.•They show high bifunctional activity for oxygen reduction and evolution reactions.•They especially improve the reversibility and cycling stability of Li–O2 batteries.Three-dimensional ordered mesoporous (3DOM) ZnCo2O4 materials have been synthesized via a hard template and used as bifunctional electrocatalysts for rechargeable Li-O2 batteries. The as-prepared ZnCo2O4 nanoparticles possess a high specific surface area of 127.2 m2 g−1 and a spinel crystalline structure. The Li-O2 battery utilizing 3DOM ZnCo2O4 shows a higher specific capacity of 6024 mAh g−1 than that with pure Ketjen black (KB). Moreover, the ZnCo2O4-based electrode enables much enhanced cyclability with a smaller discharge-recharge voltage gap than that of the carbon-only cathode. Such excellent catalytic performance of ZnCo2O4 could be associated with its larger surface area and 3D ordered mesoporous structure.

A three-dimensional (3D) graphene–Co3O4 electrode was prepared by a two-step method in which graphene was initially deposited on a Ni foam with Co3O4 then grown on the resulting graphene structure. Cross-linked Co3O4 nanosheets with an open pore structure were fully and vertically distributed throughout the graphene skeleton. The free-standing and binder-free monolithic electrode was used directly as a cathode in a Li–O2 battery. This composite structure exhibited enhanced performance with a specific capacity of 2453 mA h g−1 at 0.1 mA cm−2 and 62 stable cycles with 583 mA h g−1 (1000 mA h gcarbon−1). The excellent electrochemical performance is associated with the unique architecture and superior catalytic activity of the 3D electrode.