The application of lithium−sulfur (Li−S) batteries is severely hampered by the shuttle effect and sluggish redox kinetics. Herein, amorphous cobalt phosphide grown on a reduced graphene oxide-multiwalled carbon nanotube (rGO-CNT-CoP(A)) is designed as the sulfur host to conquer the above bottlenecks. The differences between amorphous cobalt phosphide (CoP) and crystalline CoP on the surface adsorption as well as conversion of lithium polysulfides (LiPSs) are investigated by systematical experiments and densityfunctional theory (DFT) calculations. Specifically, the amorphous CoP not only strengthens the chemical adsorption to LiPSs but also greatly accelerates liquidphase conversions of LiPSs as well as the nucleation and growth of Li 2 S. DFT calculation reveals that the amorphous CoP possesses higher binding energies and lower diffusion energy barriers for LiPSs. In addition, the amorphous CoP features reduced energy gap and the increased electronic concentrations of adsorbed LiPSs near Fermi level. These characteristics contribute to the enhanced chemisorption ability and the accelerated redox kinetics. Simultaneously, the prepared S/rGO-CNT-CoP(A) electrode delivers an impressive initial capacity of 872 mAh g −1 at 2 C and 617 mAh g −1 can be obtained after 200 cycles, exhibiting excellent cycling stability. Especially, it achieves outstanding electrochemical performance even under high sulfur loading (5.3 mg cm −2 ) and lean electrolyte (E/S = 7 μL E mg −1 S ) conditions. This work exploits the application potential for amorphous materials and contributes to the development of highly efficient Li−S batteries.

Ba deficiency is used to tune the electronic, oxygen-ion and proton conduction in BaCo0.4Fe0.4Zr0.1Y0.1O3−δ perovskite for a high-activity cathode of PCFCs.

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Mixed oxygen ionic and electronic conduction is a vital function for cathode materials of solid oxide fuel cells (SOFCs), ensuring high efficiency and low-temperature operation. However, Fe-based layered double perovskites, as a classical family of mixed oxygen ionic and electronic conducting (MIEC) oxides, are generally inactive toward the oxygen reduction reaction due to their intrinsic low electronic and oxygen-ion conductivity. Herein, Zn doping is presented as a novel pathway to improve the electrochemical performance of Fe-based layered double perovskite oxides in SOFC applications. The results demonstrate that the incorporation of Zn ions at Fe sites of the PrBaFe2O5+δ (PBF) lattice simultaneously regulates the concentration of holes and oxygen vacancies. Consequently, the oxygen surface exchange coefficient and oxygen-ion bulk diffusion coefficient of Zn-doped PBF are significantly tuned. The enhanced mixed oxygen ionic and electronic conduction is further confirmed by a lower polarization resistance of 0.0615 and 0.231 Ω·cm2 for PrBaFe1.9Zn0.1O5+δ (PBFZ0.1) and PBF, respectively, which is measured using symmetric cells at 750 °C. Moreover, the PBFZ0.1-based single cell demonstrates the highest output performance among the reported Fe-based layered double perovskite cathodes, rendering a peak power density of 1.06 W·cm–2 at 750 °C and outstanding stability over 240 h at 700 °C. The current work provides a highly effective strategy for designing cathode materials for next-generation SOFCs.

Protonic ceramic fuel cells (PCFCs) are receiving increasing attention because of their high energy conversion efficiency. However, traditional mixed oxygen-ionic and electronic conductors (MOECs) show sluggish oxygen reduction kinetics when used in PCFCs because of their intrinsic low protonic conductivity. Herein, it is reported that cooperatively regulating the concentration and basicity of oxygen vacancies can result in fast proton transport in MOECs, which is demonstrated in a Zr 4+ -doped Sr 2 Fe 1.5 Mo 0.5 O 6−δ (SFMZ) perovskite. The so-obtained SFMZ perovskite renders plentiful oxygen vacancies and strong hydration ability, which can boost the formation of protonic defects. Furthermore, the chemical diffusion coefficient of protons (D H,chem ) is established first to determine the proton mobility of the cathode. The results indicate that SFMZ exhibits improved proton diffusion kinetics with a D H,chem value of 8.71 × 10 −7 cm 2 s −1 at 700 °C, comparable to the diffusion coefficient of the commonly used protonic electrolyte BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ of 1.84 × 10 −6 cm 2 s −1 . A low polarization resistance of 0.169 Ω cm 2 and a peak power density as high as 0.79 W cm −2 were achieved at 700 °C with the SFMZ cathode. Such excellent performance suggests that rationally tailoring the oxygen vacancy is a feasible strategy to promote proton diffusion in perovskite-structured electrode materials as efficient PCFC cathodes.

Defective materials have been demonstrated to possess adsorptive and catalytic properties in lithium–sulfur (Li–S) batteries, which can effectively solve the problems of lithium polysulfides (LiPSs) shuttle and sluggish conversion kinetics during charging and discharging of Li–S batteries. However, there is still a lack of research on the quantitative relationship between the defect concentration and the adsorptive‐catalytic performance of the electrode. In this work, perovskites Sr0.9Ti1−xMnxO3−δ (STMnx) (x = 0.1–0.3) with different oxygen‐vacancy concentrations are quantitatively regulated as research models. Through a series of tests of the adsorptive property and electrochemical performance, a quantitative relationship between oxygen‐vacancy concentration and adsorptive‐catalytic properties is established. Furthermore, the catalytic mechanism of oxygen vacancies in Li–S batteries is investigated using density functional theory calculations and in situ experiments. The increased oxygen vacancies can effectively increase the binding energy between perovskite and LiPSs, reduce the energy barrier of LiPSs decomposition reaction, and promote LiPSs conversion reaction kinetics. Therefore, the perovskite STMn0.3 with high oxygen‐vacancy concentrations exhibits excellent LiPSs adsorptive and catalytic properties, realizing high‐efficiency Li–S batteries. This work is helpful to realize the application of the quantitative regulation strategy of defect engineering in Li–S batteries.

Hierarchical porous three-dimensional MnCoO 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-O cell applications. This system showed a high discharge capacity of up to 12 919 mAh g at 0.1 mA cm and excellent rate capability. Under constrained specific capacities of 500 and 1000 mAh g, Li-O 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 MnCoO 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-O 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-O cells have been explored. Furthermore, the nucleation process of the discharge product morphology has been investigated.

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are both fundamental and essential processes for various energy conversion and storage systems. The kinetics of ORR and OER play a critical role in their energy efficiency and practicality. Here, flower-like ultrathin Co3O4 nanosheets synthesized through a facile solvothermal technique were studied as a bifunctional catalyst for both water splitting and non-aqueous Li-O2 batteries. Due to the novel structure and highly active {110} and {100} exposed facets, which can effectively facilitate mass transfer and enhance catalytic capability, Co3O4 nanosheets exhibit better stability and higher ORR/OER activity than Co3O4 nanoparticles, Co3O4 bulks, Pt/C, and RuO2 in alkaline solution. More importantly, Li-O2 batteries with ultrathin Co3O4 nanosheets catalyst can enhance the initial discharge capacity from 6400 to 8600 mA h g-1 and improve the cyclability up to 160 cycles at 500 mA g-1. Unexpectedly, XRD and UV/Vis techniques suggest that the main product in Co3O4 nanosheets based cathodes is LiOH, with resulting LiOH also demonstrating reversible formation/decomposition behavior, rather than Li2O2 in pure Super P based cathodes. Further investigation confirms that Co3O4 can also catalyze the electrolyte decomposition responsible for the formation of LiOH, and a reaction mechanism was illustrated. This work highlights that the traditional high-efficiency bifunctional catalyst in aqueous media may not be suitable for non-aqueous Li-O2 batteries, and the effect of catalyst on electrolyte besides the discharge product should also be carefully considered for the design of more stable and practical Li-O2 systems.