Micropore engineering on hollow nanospheres for ultra-stable sodium-selenium batteries

Attracted by high energy density and considerable conductivity of selenium(Se),Na-Se batteries have been deemed promising energy-storage systems.But,it still suffers from sluggish kinetic behaviors and similar“shuttling effect”to S-electrodes.Herein,utilizing uniform hollow carbon spheres as precursors,Se-material is effectively loaded through vapor-infiltration method.Owing to the distribution of optimized pores,the content of microspores could be up to~60%(<2 nm),serving important roles for the physical confinement effect.Meanwhile,the rich oxygen-containing groups and N-elements could be noted,inducing the evolution of electron-moving behaviors.More significantly,assisted by the interfacial C-Se bonds and tiny Se distributions,Se electrodes are activated during cycling.Used as cathodes for Na-Se systems,the as-resulted samples display a capacity of 593.9 mA h g^(-1)after 100 cycles at the current density of 0.1 C.Even after 6000 cycles,the capacity could be still kept at about 225 mA h g^(-1)at 5.0 C.Supported by the detailed kinetic analysis,the designed microspores size induces the increasing redox reaction of nano Se,whilst the surface traits further render the enhancement of pseudo-capacitive contributions.Moreover,after cycling,the product Sex(x<4)in pores serves as the primary active material.Given this,the work is anticipated to provide an effective strategy for advanced electrodes for Na-Se systems.

Engineering the morphology/porosity of oxygen-doped carbon for sulfur host as lithium-sulfur batteries

Despite the intriguing merits of lithium-sulfur(Li-S) systems, they still suffer from the notorious‘‘shuttling-effect" of polysulfides. Herein, carbon materials with rational tailoring of morphology and pores were designed for strong loading/adsorption with the controlling of energy-storage ability.Through rational tailoring, it is strongly verified that such engineering of evolutions result in variational of sulfur immobilization in the obtained carbon. As expected, the targeted sample delivers a stable capacity of 925 m Ah g^(-1) after 100 loops. Supporting by the "cutting-off" manners, it is disclosed that mesopores in carbon possess more fascinated traits than micro/macropores in improving the utilization of sulfur and restraining Li_(2)S_x(4≤x≤8). Moreover, the long-chain polysulfide could be further consolidated by auto-doping oxygen groups. Supported by in-depth kinetic analysis, it is confirmed that the kinetics of ion/e-transfer during charging and discharging could be accelerated by mesopores, especially in stages of the formation of solid S_(8) and Li_(2)S, further improving the capacity of ion-storage in Li-S battery. Given this, the elaborate study provide significant insights into the effect of pore structure on kinetic performance about Li-storage behaviors in Li-S battery, and give guidance for improving sulfur immobilization.

Delicate chemical structure regulation of nonfullerene acceptor for efficient and large thickness organic solar cells

Inspired by the success of CH-series acceptors, a small-molecular acceptor, CH-Tz was reported by adopting a new conjugationextended electron-deficient unit([1,2,5]thiadiazolo[3,4-b]pyrazine) on the central core. Owing to the enhanced inter-/intramolecular interactions, CH-Tz exhibited near-infrared absorption and an effective three-dimensional molecular packing network in its single crystal. When blended with polymer donor PM6, the binary device achieved a high power conversion efficiency(PCE) of 18.54%, with a notable short-circuit current density(J_(sc)) of 27.54 m A cm-2and an excellent fill factor(FF) over 80%,which can be partly ascribed to the balanced charge transport properties in the blend film. After employing D18-Cl as the third component, an enhanced PCE of 18.85% was achieved due to a more obvious fiber network. Impressively, the CH-Tz-based OSC devices show excellent thermal stability and thickness insensitivity. Record-breaking Jscof 28.92 m A cm-2was reached for PM6:D18-Cl:CH-Tz ternary device with a thickness of 560 nm. Besides, CH-Tz shows potential in fabricating multicomponent high-performance organic solar cells, where over 19% efficiency could be realized in the quaternary device. Our work advances the strong influence of electron-deficient central units on molecular photovoltaic properties and guides the design of acceptors for stable and large-thickness organic solar cells.