Bimetallic Sulfide Sb2S3/FeS2 Heterostructure Anchored in a Carbon Skeleton for Fast and Stable Sodium Storage.

Sodium-ion batteries (SIBs) are a promising substitute for lithium batteries due to their abundant resources and low cost. Metal sulfides are regarded as highly attractive anode materials due to their superior mechanical stability and high theoretical specific capacity. Guided by the density functional theory (DFT) calculations, 3D porous network shaped Sb2S3/FeS2 composite materials with reduced graphene oxide (rGO) through a simple solvothermal and calcination method, which is predicted to facilitate favorable Na+ ion diffusion, is synthesized. Benefiting from the well-designed structure, the resulting Sb2S3/FeS2 exhibit a remarkable reversible capacity of 536 mAh g-1 after 2000 cycles at a current density of 5 A g-1 and long high-rate cycle life of 3000 cycles at a current density of 30 A g-1 as SIBs anode. In situ and ex situ analyses are carried out to gain further insights into the storage mechanisms and processes of sodium ions in Sb2S3/FeS2@rGO composites. The significantly enhanced sodium storage capacity is attributed to the unique structure and the heterogeneous interface between Sb2S3 and FeS2. This study illustrates that combining rGO with heterogeneous engineering can provide an ideal strategy for the synthesis of new hetero-structured anode materials with outstanding battery performance for SIBs.

Honeycomb-Structured MoSe2 /rGO Composites as High-Performance Anode Materials for Sodium-Ion Batteries.

Sodium-ion batteries are a promising substitute for lithium batteries due to the abundant resources and low cost of sodium. Herein, honeycomb-shaped MoSe2 /reduced graphene oxide (rGO) composite materials are synthesized from graphene oxide (GO) and MoSe2 through a one-step solvothermal process. Experiments show that the 3D honeycomb structure provides excellent electrolyte penetration while alleviating the volume change during electrochemical cycling. An anode prepared with MoSe2 /rGO composites exhibits significantly improved sodium-ion storage properties, where a large reversible capacity of 215 mAh g-1 is obtained after 2700 cycles at the current density of 30.0 A g-1 or after 5900 cycles at 8.0 A g-1 . When such an anode is paired with Na3 V2 (PO4 )3 to form a full cell, a reversible specific capacity of 107.5 mAh g-1 can be retained after 1000 cycles at the current of 1.0 A g-1 . Transmission electron microscopy, X-ray photoelectron spectroscopy and in situ X-ray diffraction (XRD) characterization reveal the reversible storage reaction of Na ions in the MoSe2 /rGO composites. The significantly enhanced sodium storage capacity is attributed to the unique honeycomb microstructure and the use of ether-based electrolytes. This study illustrates that combining rGO with ether-based electrolytes has tremendous potential in constructing high-performance sodium-ion batteries.

Strong single-photon optomechanical coupling in a hybrid quantum system.

Engineering strong single-photon optomechanical couplings is crucial for optomechanical systems. Here, we propose a hybrid quantum system consisting of a nanobeam (phonons) coupled to a spin ensemble and a cavity (photons) to overcome it. Utilizing the critical property of the lower-branch polariton (LBP) formed by the ensemble-phonon interaction, the LBP-cavity coupling can be greatly enhanced by three orders magnitude of the original one, while the upper-branch polariton (UBP)-cavity coupling is fully suppressed. Our proposal breaks through the condition of the coupling strength less than the critical value in previous schemes using two harmonic oscillators. Also, strong Kerr effect can be induced in our proposal. This shows our proposed approach can be used to study quantum nonlinear and nonclassical effects in weakly coupled optomechanical systems.