Multifunctional Heterostructured Fe3 O4 -FeTe@MCM Electrocatalyst Enabling High-Performance Practical Lithium-Sulfur Batteries Via Built-in Electric Field.

The development of capable of simultaneously modulating the sluggish electrochemical kinetics, shuttle effect, and lithium dendrite growth is a promising strategy for the commercialization of lithium-sulfur batteries. Consequently, an elaborate preparation method is employed to create a host material consisting of multi-channel carbon microspheres (MCM) containing highly dispersed heterostructure Fe3 O4 -FeTe nanoparticles. The Fe3 O4 -FeTe@MCM exhibits a spontaneous built-in electric field (BIEF) and possesses both lithophilic and sulfophilic sites, rendering it an appropriate host material for both positive and negative electrodes. Experimental and theoretical results reveal that the existence of spontaneous BIEF leads to interfacial charge redistribution, resulting in moderate polysulfide adsorption which facilitates the transfer of polysulfides and diffusion of electrons at heterogeneous interfaces. Furthermore, the reduced conversion energy barriers enhanced the catalytic activity of Fe3 O4 -FeTe@MCM for expediting the bidirectional sulfur conversion. Moreover, regulated Li deposition behavior is realized because of its high conductivity and remarkable lithiophilicity. Consequently, the battery exhibited long-term stability for 500 cycles with 0.06% capacity decay per cycle at 5 C, and a large areal capacity of 7.3 mAh cm-2 (sulfur loading: 9.73 mg cm-2 ) at 0.1 C. This study provides a novel strategy for the rational fabrication of heterostructure hosts for practical Li-S batteries.

Biodegradable Microcapsules Prepared by Self-Healing of Porous Microspheres.

A method is herein proposed to produce biodegradable microcapsules by a self-healing of porous microspheres, which were prepared from water-in-oil-in-water (W1/O/W2) double-emulsion templates. Methoxypoly(ethylene glycol)-b-poly-dl-lactide (PELA) was dissolved in ethyl acetate (EA) as the oil phase (O) of double emulsion, NaCl and poly(vinyl acetate) aqueous solutions serving as internal and external water phases (W1 and W2), respectively. Porous PELA microspheres were prepared by a two-step emulsification and solvent extraction method. Core materials, such as proteins or latex particles, could then be loaded by diffusion from the external water phase. Eventually, the pores in the surface could heal up triggered by a solvent swelling or infrared irradiation to form closed microcapsules. Compared with traditional encapsulations which are based on the two-step emulsification, the proposed posthealing approach could overcome some drawbacks, such as the shear destruction, solvent erosion to delicate core materials, or even their unexpected release during the emulsification. Besides PELA, poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) microcapsules were also proved feasible to fulfill such an approach.