Carbon-Coated ZnS-FeS2 Heterostructure as an Anode Material for Lithium-Ion Battery Applications.

The construction of carbon-coated heterostructures of bimetallic sulfide is an effective technique to improve the electrochemical activity of anode materials in lithium-ion batteries. In this work, the carbon-coated heterostructured ZnS-FeS2 is prepared by a two-step hydrothermal method. The crystallinity and nature of carbon-coating are confirmed by the investigation of XRD and Raman spectroscopy techniques. The nanoparticle morphology of ZnS and plate-like morphology of FeS2 is established by TEM images. The chemical composition of heterostructure ZnS-FeS2@C is discovered by an XPS study. The CV results have disclosed the charge storage mechanism, which depends on the capacitive and diffusion process. The BET surface area (37.95 m2g-1) and lower Rct value (137 Ω) of ZnS-FeS2@C are beneficial to attain higher lithium-ion storage performance. It delivered a discharge capacity of 821 mAh g-1 in the 500th continuous cycle @ A g-1, with a coulombic efficiency of around 100%, which is higher than the ZnS-FeS2 heterostructure (512 mAh g-1). The proposed strategy can improve the electrochemical performance and stability of lithium-ion batteries, and can be helpful in finding highly effective anode materials for energy storage devices.

A Flower-like In2O3 Catalyst Derived via Metal-Organic Frameworks for Photocatalytic Applications.

The most pressing concerns in environmental remediation are the design and development of catalysts with benign, low-cost, and efficient photocatalytic activity. The present study effectively generated a flower-like indium oxide (In2O3-MF) catalyst employing a convenient MOF-based solvothermal self-assembly technique. The In2O3-MF photocatalyst exhibits a flower-like structure, according to morphology and structural analysis. The enhanced photocatalytic activity of the In2O3-MF catalyst for 4-nitrophenol (4-NP) and methylene blue (MB) is likely due to its unique 3D structure, which includes a large surface area (486.95 m2 g-1), a wide spectrum response, and the prevention of electron-hole recombination compared to In2O3-MR (indium oxide-micro rod) and In2O3-MD (indium oxide-micro disc). In the presence of NaBH4 and visible light, the catalytic performances of the In2O3-MF, In2O3-MR, and In2O3-MD catalysts for the reduction of 4-NP and MB degradation were investigated. Using In2O3-MF as a catalyst, we were able to achieve a 99.32 percent reduction of 4-NP in 20 min and 99.2 percent degradation of MB in 3 min. Interestingly, the conversion rates of catalytic 4-NP and MB were still larger than 95 and 96 percent after five consecutive cycles of catalytic tests, suggesting that the In2O3-MF catalyst has outstanding catalytic performance and a high reutilization rate.

Improved High Rate and Temperature Stability Using an Anisotropically Aligned Pillar-Type Solid Electrolyte Interphase for Lithium-Ion Batteries.

Numerous reports have elucidated the advantages of SiOx-based anodes including their large capacities and superior cycling stabilities. However, these electrodes have not been optimized for use in electric vehicles (EVs), which demand even better performance stability at fast charging rates and high temperatures. Herein, we fabricated a novel solid electrolyte interphase (SEI) using nanodiamondseeds. The grown SEI comprised an assembly of pillars, with a height and diameter of approximately 600 and 250 nm, respectively. As a result, the Li||Ti-SiOx@C cell with a nanodiamond-containing electrolyte achieved a high capacity retention of 76.4% over 1000 cycles at 5 A g-1 and 50 °C, whereas the cell with no nanodiamond seeds showed a severe decay in the capacity and retained only 61.5% of its initial capacity. Furthermore, the NCM811||Ti-SiOx@C full cell constructed with the pillar-type SEI also showed a high capacity retention of 61.8% at 5 C (1 C = 200 mAh g-1) and 50 °C after 500 cycles, which was a significant improvement from the value (33.3%) demonstrated by its counterpart comprising the conventional SEI. The results obtained herein will enable the development of high-performance lithium-ion batteries.

Fabrication of a Nondegradable Si@SiO x /n-Carbon Crystallite Composite Anode for Lithium-Ion Batteries.

A Si-based anode maintaining its high electrochemical performance with cycles was prepared for the nondegradable lithium-ion battery. Nanoscaled Si particles were mechanochemically coupled with approximately 3 nm thick oxide layer and n-carbon (nanoscaled carbon) crystallites to overcome silicon's inherent problems of poor electronic conductivity and severe volume change during lithiation and delithiation cycling. The oxide layer of SiO x was chemically formed via a controlled oxygen environment during the process; meanwhile, the n-carbon crystallites were obtained by mechanical fragmentation from ∼70 µm sized multilayered graphene powders with a low degree of agglomeration. The Si-based composite anode, processed by the above-mentioned mechanochemical coupling, maintained a superior discharge capacity of 1767 mA h/g through 100 cycles with a Coulombic efficiency exceeding 98% at a current density of 100 mA/g. According to our current study, the coupling of the Si particles with oxide layer and n-carbon crystallites was found to be a significantly efficient way to prevent the performance degradation of the Si-based anode.

Preparation of carbon blacks by liquid phase plasma (LPP) process.

In this study, carbon black nanoparticles were synthesized by Liquid Phase Plasma (LPP) technique; plasma generated in the organic solvent of benzene at 4.9 kV with the pulse frequency of 15 kHz and width of 5 micros transformed the carbon atoms in the solvent into carbon blacks by oxidation and reduction reactions. Graphite phase was found to be introduced into the carbon blacks without any additional processes due to the characteristics of LPP process, resulting in a higher G/D ratio of 0.92, compared to 0.83 of commercial Ketjen carbon blacks. For the performance improvement, heat treatment was employed and its parameters such as temperature and duration time were optimized in relation to the crystallinity and specific surface area of the carbon blacks. Carbon blacks heat treated at 450 degrees C in the air for 20 min were measured to have the discharge capacity of 1750 mAh/g and irreversible charging and discharging capacity ratio of 52.6%.

Enhanced water splitting by Fe2O3-TiO2-FTO photoanode with modified energy band structure.

The effect of TiO2 layer applied to the conventional Fe2O3/FTO photoanode to improve the photoelectrochemical performance was assessed from the viewpoint of the microstructure and energy band structure. Regardless of the location of the TiO2 layer in the photoanodes, that is, Fe2O3/TiO2/FTO or TiO2/Fe2O3/FTO, high performance was obtained when α-Fe2O3 and H-TiNT/anatase-TiO2 phases existed in the constituent Fe2O3 and TiO2 layers after optimized heat treatments. The presence of the Fe2O3 nanoparticles with high uniformity in the each layer of the Fe2O3/TiO2/FTO photoanode achieved by a simple dipping process seemed to positively affect the performance improvement by modifying the energy band structure to a more favorable one for efficient electrons transfer. Our current study suggests that the application of the TiO2 interlayer, together with α -Fe2O3 nanoparticles present in the each constituent layers, could significantly contribute to the performance improvement of the conventional Fe2O3 photoanode.