Rechargeable lithium–sulfur (Li–S) batteries are receiving ever‐increasing attention due to their high theoretical energy density and inexpensive raw sulfur materials. However, their rapid capacity fade has been one of the key barriers for their further improvement. It is well accepted that the major degradation mechanisms of S‐cathodes include low electrical conductivity of S and sulfides, precipitation of nonconductive Li2S2 and Li2S, and poly‐shuttle effects. To determine these degradation factors, a comprehensive study of sulfur cathodes with different amounts of electrolytes is presented here. A survey of the fundamentals of Li–S chemistry with respect to capacity fade is first conducted; then, the parameters obtained through electrochemical performance and characterization are used to determine the key causes of capacity fade in Li–S batteries. It is confirmed that the formation and accumulation of nonconductive Li2S2/Li2S films on sulfur cathode surfaces are the major parameters contributing to the rapid capacity fade of Li–S batteries.

Designing stable and efficient electrocatalysts for both oxygen reduction and evolution reactions (ORR/OER) at low‐cost is challenging. Here, a carbon‐based bifunctional catalyst of magnetic catalytic nanocages that can direct enhance the oxygen catalytic activity by simply applying a moderate (350 mT) magnetic field is reported. The catalysts, with high porosity of 90% and conductivity of 905 S m−1, are created by in situ doping metallic cobalt nanodots (≈10 nm) into macroporous carbon nanofibers with a facile electrospinning method. An external magnetic field makes the cobalt magnetized into nanomagnets with high spin polarization, which promote the adsorption of oxygen‐intermediates and electron transfer, significantly improving the catalytic efficiency. Impressively, the half wave‐potential is increased by 20 mV for ORR, and the overpotential at 10 mA cm−2 is decreased by 15 mV for OER. Compared with the commercial Pt/C+IrO2 catalysts, the magnetic catalyzed Zn–air batteries deliver 2.5‐fold of capacities and exhibit much longer durability over 155 h. The findings point out a very promising strategy of using electromagnetic induction to boost oxygen catalytic activity.

This review systematically summarized Li-rich layered oxides and states the strategies to enhance such materials when used in Li-ion batteries.

Layered Li(Ni 1−x−y Mn x Co y )O 2 (NMC) oxides are promising cathode materials capable of addressing some of the challenges associated with next-generation energy storage devices. In particular, improved energy densities, longer cycle-life, and improved safety characteristics with respect to current technologies are needed. However, sufficient knowledge on the atomic-scale processes governing these metrics in working cells is still lacking. Herein, density functional theory (DFT) is employed to predict the stability of several low-index surfaces of Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 (NMC111) as a function of Li and O chemical potentials. Predicted particle shapes are compared with those of single crystal NMCs synthesized under different conditions. The most stable surfaces for stoichiometric NMC111 are predicted to be the nonpolar (104), the polar (012) and (001), and the reconstructed, polar (110) surfaces. Results indicate that intermediate spin Co 3+ ions lower the (104) surface energy. Furthermore, it was found that removing oxygen from the (012) surface was easier than from the (104) surface, suggesting a facet dependence on surface-oxygen vacancy formation. These results give important insights into design criteria for the rational control of synthesis parameters as well as establish a foundation on which future mechanistic studies of NMC surface instabilities can be developed.

Conductive porous carbon nanofibers are promising for environmental, energy, and catalysis applications. However, increasing their porosity and conductivity simultaneously remains challenging. Here we report chemical crosslinking electrospinning, a macro–micro dual-phase separation method, to synthesize continuous porous carbon nanofibers with ultrahigh porosity of >80% and outstanding conductivity of 980 S cm−1. With boric acid as the crosslinking agent, poly(tetrafluoroethylene) and poly(vinyl alcohol) are crosslinked together to form water-sol webs, which are then electrospun into fibrous films. After oxidation and pyrolysis, the as-spun fibers are converted into B-F-N triply doped porous carbon nanofibers with well-controlled macro–meso–micro pores and large surface areas of ~750 m2 g−1. The sponge-like porous carbon nanofibers with substantially reduced mass transfer resistances exhibit multifunction in terms of gas adsorption, sewage disposal, liquid storage, supercapacitors, and batteries. The reported approach allows green synthesis of high-performance porous carbon nanofibers as a new platform material for numerous applications.

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Self-standing photocatalytic membranes constructed from TiO2 nanofibers hold great promise in environmental remediation; however, challenges still remained for the poor mechanical properties of polycrystalline TiO2 nanofibers. Herein, soft Zr-doped TiO2 (TZ) nanofibrous membranes with robust mechanical properties and enhanced photocatalytic activity were fabricated via electrospinning technique. The Zr4+ incorporation could effectively inhibit the grain growth and reduce the surface defects and breaking point of TiO2 nanofiber. The as-prepared TZ membranes were composed of well-interconnected nanofibers with a high aspect ratios, small grain size and pore size, which exhibited good tensile strength (1.32 MPa) and showed no obvious damage after 200 cycles of bending to a radius of 2 mm. A plausible bending deformation mechanism of the soft TZ membranes was proposed from microscopic single nanofiber to macroscopical membranes. Moreover, the resultant TZ membranes displayed better photocatalytic performance for methylene blue degradation compared to a commercial catalyst (P25), including high degradation degree of 95.4% within 30 min, good reusability in 5 cycles, and easiness of recycling. The successful preparation of such fascinating materials may open up new avenues for the design and development of soft TiO2-based membranes for various application.

BaTiO 3 crystals are attractive materials due to their high dielectric properties, but they are brittle and inelastic ceramics, which limits their broader applications in emerging fields, such as flexible electronics. A scalable strategy for the fabrication of ultra-flexible crystalline BaTiO 3 nanofiber (NF) films by a sol-gel electrospinning method, followed by a brief calcination, is reported. It facilitates the formation of perovskite BaTiO 3 crystals with intricate grain boundaries at a low temperatures by growing them within polymer NF templates. The ceramic films have a polymer-like softness of 50 mN, a large Young's modulus of 61 MPa, and an elastic strain of 0.9%. Moreover, they have a low density of 28 mg cm −3 and demonstrate superior softness without fracture after deformation. Piezoelectric sensors fabricated based on these films exhibit a high sensitivity of 80 ms with an output voltage of 1.05 V at a pressure of 100 kPa. This approach allows for the largescale fabrication of flexible BaTiO 3 crystal NF films.