Nitrogen-doped hierarchical porous carbon derived from metal–organic aerogel for high performance lithium–sulfur batteries

Nitrogen-doped three-dimensional(3 D) porous carbon materials have numerous applications due to their highly porous structures, abundant structural nitrogen heteroatom decoration and low densities. Herein,nitrogen doped hierarchical 3 D porous carbons(NHPC) were prepared via a novel metal–organic aerogel(MOA), using hexamethylenetetramine(HMT), 1,3,5-benzenetricarboxylic acid and copper(II) as starting materials. The morphology, porous structure of the building blocks in the NHPC can be tuned readily using different amount of HMT, which makes elongation of the pristine octahedron of HKUST-1 to give rise to different aspect ratio rod-like structures. The as-prepared NHPC with rod-like carbons exhibit high performance in lithium sulfur battery due to the rational ion transfer pathways, high N-doped doping and hierarchical porous structures. As a result, the initial specific capacity of 1341 m A h/g at rate of 0.5 C(1 C = 1675 m A h/g) and high-rate capability of 354 m A h/g at 5 C was achieved. The decay over 500 cycles is 0.08% per cycle at 1 C, highlighting the long-cycle Li–S batteries.

Electrolyte/Structure‑Dependent Cocktail Mediation Enabling High‑Rate/Low‑Plateau Metal Sulfide Anodes for Sodium Storage

As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-stringed metal sulfides superstructure(CSC)assembled by nano-dispersed SnS_(2) and CoS_(2) phases,cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges.The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect,enabling the circumvention of intrinsic drawbacks of different metal sulfides.By utilizing ether-based electrolyte,the reversibility of metal sulfides is greatly improved,sustaining a long-life effectivity of cocktail-like mediation.As such,CSC effectively overcomes low-rate flaw of SnS_(2) and highplateau demerit of CoS_(2),simultaneously realizes a high rate and a low plateau.In half-cells,CSC delivers an ultrahigh-rate capability of 327.6 mAh g^(−1) anode at 20 A g^(−1),far outperforming those of monometallic sulfides(SnS_(2),CoS_(2))and their mixtures.Compared with CoS_(2) phase and SnS_(2)/CoS_(2) mixture,CSC shows remarkably lowered average charge voltage up to ca.0.62 V.As-assembled CSC//Na1.5VPO4.8F0.7 full-cell shows a good rate capability(0.05~1.0 A g^(−1),120.3 mAh g^(−1) electrode at 0.05 A g^(−1))and a high average discharge voltage up to 2.57 V,comparable to full-cells with alloy-type anodes.Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC,compared with single phase and mixed phases.Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS_(2) and CoS_(2) phases are responsible for the lowered charge voltage of CSC.This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes,which will boost the development of high-rate/-voltage sodium-ion full batteries.

Recovery of Copper from Copper Sulfide Concentrate by Sulfation Roasting

Sulfation roasting was studied to extract copper from the copper sulfide concentrate. Sodium sulfite was added as sulfation agent to the copper sulfide concentrate during roasting in this study. Sulfur removal rate at different roasting temperatures was investigated, and the effects of roasting temperature, roasting time, and the amount of sodium sulfite on copper extraction were studied. Copper extraction higher than 96% was achieved at optimum roasting conditions.