Nitrogen/sulfur dual-doping of reduced graphene oxide harvesting hollow ZnSnS3 nano-microcubes with superior sodium storage

Bimetallic sulfides have exhibited promising applications in advanced sodium-ion batteries (SIBs) due to their relatively high electronic conductivity and electrochemical activity. In this study, for the first time, the N/S dual-doped reduced graphene oxide (rGO) encapsulating hollow ZnSnS3 nano-microcubes (N/S-rGO@ZnSnS3) is designed to improve the sluggish reaction kinetics, poor cycling stability and unsatisfactory rate capability of metal sulfides. To examine this design, the cycling stability and rate capability of the desired anode material is studied in detail. It is found that N/S-rGO@ZnSnS3 hybrid delivers a high discharge capacity of 501.7 mAh g−1 after 100 cycles at 0.1 A g−1, and a reversible capacity of 290.7 mAh g−1 after 500 cycles at 1.0 A g−1 with a capacity fading of 0.06% per cycle. The cycling stability as well as rate capability of N/S-rGO@ZnSnS3 are superior to those of the pristine hollow ZnSnS3 cubes/un-doped rGO composite. It is convinced that the electrode performance is strongly rooted in its structural conformation. Furthermore, the structural evolutions of ZnSnS3 reactions with sodium are revealed by in situ X-ray diffraction combined with ex situ X-ray photoelectron spectroscopy, which provides a valuable revelation for the understanding of reaction mechanism toward bimetallic sulfides and beyond

Evaluating the surface properties of HA coating on Co-Cr based alloy substrate

Hydroxyapatite (HA) is the main structural component of natural bone and due to its excellent biocompatibility and bioactivity it can be used in biomedical application as a coating layer for metallic implants to help formation of chemical bonding at HA/bone interface and work as a protective layer against ion release from a metallic prosthesis. In this study, HA bioactive coating was created using sol-gel method on the high carbon CoCrMo substrate. Although sol-gel is simple and cost effective method with capability to control chemical composition and able to coat on the complex-shape implants, massive cracks of HA sol-gel coated layer on implants are still the major issue. Cracks can be minimized by changing the viscosity, composition or variation in heat treatment procedure. In this study, Na3PO4 and CaCl2 were used as the main precursors in sol-gel preparation. The sol-gel was centrifuged at three different speeds (1500, 1750 and 2000 rpm). Coated specimens were sintered at 500°C, 600°C and 700°C for 20 minutes and 1 hour respectively. HA coated samples were analyzed under FESEM, XRD, AFM and electrochemical corrosion tests. The initial FESEM test revealed that the best centrifuging speed that results in a crack free HA coated layer at room temperature is 1750 rpm with viscosity of 1798 CP. The FESEM and XRD results also revealed that the best surface morphology with semi-crystalline microstructure belong to the sample sintered at 600°C for 20 min. Also it is concluded that sintering temperature above 600°C for HA coating on Co-Cr based alloys results in cracks propagation. Moreover, in terms of surface roughness all coated and sintered samples except the one sintered at 500°C for 20 min, showed a good result as well. Finally, in terms of corrosion resistance the sample sintered at 600°C for 20 min showed the corrosion rate almost 3.5 times lesser than uncoated sample

Revealing the Self-Generated Heterointerface of NaV₂O₅ in Zn Storage via a Scalable Production Method

Solid-state sintering has been widely used as the most typical preparation method for nanomaterials. However, it usually requires high-pressure and high-temperature conditions because a slow solid-state diffusion kinetics and the presence of pores would impede proper ion diffusion. Herein, a simple and scalable method, so-called template-assisted solid-state sintering, has been utilized to synthesize a two-dimensional (2D) lamellar NaV2O5 as a cathode for aqueous zinc-ion batteries (AZIBs), and its mechanism of the improved preparation method is explored. A combined series of in situ/ex situ measurements and density functional theory (DFT) calculation reveal the Zn storage mechanism of the Zn//NaV2O5 system. A new phase of Zn3(OH)2V2O7(H2O)2 will be irreversibly generated, resulting in a self-generated heterointerface of Zn3(OH)2V2O7(H2O)2/NaV2O5. It will tune the electronic structure of NaV2O5 and accelerate the diffusion of Zn in the bulk phase, which inspires regulation of its generation for beneficial effects. In addition, a self-healing quasi-solid battery using the designed cathode has been assembled to demonstrate its application in the field of flexible wearables. This work offers a novel concept and path for creating the cathode materials for high-performance aqueous/nonaqueous batteries