A Low-Cost and Scalable Carbon Coated SiO-Based Anode Material for Lithium-Ion Batteries

A Hybrid Structure to Improve Electrochemical Performance of SiO Anode Materials in Lithium-Ion Battery

The wide utilization of lithium-ion batteries (LIBs) prompts extensive research on the anode materials with large capacity and excellent stability. Despite the attractive electrochemical properties of pure Si anodes outperforming other Si-based materials, its unsafety caused by huge volumetric expansion is commonly admitted. Silicon monoxide (SiO) anode is advantageous in mild volume fluctuation, and would be a proper alternative if the low initial columbic efficiency and conductivity can be ameliorated. Herein, a hybrid structure composed of active material SiO particles and carbon nanofibers (SiO/CNFs) is proposed as a solution. CNFs, through electrospun processes, serve as a conductive skeleton for SiO nanoparticles and enable SiO nanoparticles to be uniformly embedded in. As a result, the SiO/CNF electrochemical performance reaches a peak at 20% the mass ratio of SiO, where the retention rate reaches 73.9% after 400 cycles at a current density of 100 mA g-1, and the discharge capacity after stabilization and 100 cycles are 1.47 and 1.84 times higher than that of pure SiO, respectively. A fast lithium-ion transport rate during cycling is also demonstrated as the corresponding diffusion coefficient of the SiO/CNF reaches ~8 × 10-15 cm2 s-1. This SiO/CNF hybrid structure provides a flexible and cost-effective solution for LIBs and sheds light on alternative anode choices for industrial battery assembly.

A highly conductive and robust micrometre-sized SiO anode enabled by an in situ grown CNT network with a safe petroleum ether carbon source

SiO-based materials as lithium-ion anodes have attracted huge attention owing to their ultrahigh capacity. However, they usually undergo severe volume expansion over the repeated lithiation/delithiation processes and have low electronic conductivity, leading to an inferior cycling stability and poor rate capability. In this study, carbon nanotubes in situ grown on the surface of commercially available micro-sized SiO (D50 = 5 μm) were prepared. The conductive network composed of one-dimensional carbon nanotubes could enhance its conductivity and enhance the structural stability during the cycling. The synthesized 3D-SiO@C material demonstrates good long-term cycling stability, with a reversible capacity of up to 687.7 mA h g-1 after 1000 cycles, and it maintains a high reversible capacity of 736.8 mA h g-1, even at a high current density of 1 A g-1.

Distinctive Electric Properties of Group 14 Oxides: SiO2, SiO, and SnO2

The oxides of group 14 have been widely used in numerous applications in glass, ceramics, optics, pharmaceuticals, and food industries and semiconductors, photovoltaics, thermoelectrics, sensors, and energy storage, namely, batteries. Herein, we simulate and experimentally determine by scanning kelvin probe (SKP) the work functions of three oxides, SiO2, SiO, and SnO2, which were found to be very similar. Electrical properties such as electronic band structure, electron localization function, and carrier mobility were also simulated for the three crystalline oxides, amorphous SiO, and surfaces. The most exciting results were obtained for SiO and seem to show Poole-Frankel emissions or trap-assisted tunneling and propagation of surface plasmon polariton (SPP) with nucleation of solitons on the surface of the Aluminum. These phenomena and proposed models may also describe other oxide-metal heterojunctions and plasmonic and metamaterials devices. The SiO2 was demonstrated to be a stable insulator interacting less with the metals composing the cell than SnO2 and much less than SiO, configuring a typical Cu/SiO2/Al cell potential well. Its surface charge carrier mobility is small, as expected for an insulator. The highest charge carrier mobility at the lowest conduction band energy is the SnO2's and the most symmetrical the SiO's with a similar number of electron holes at the conduction and valence bands, respectively. The SnO2 shows it may perform as an n-type semiconductor.

pH-Regulated Refinement of Pore Size in Carbon Spheres for Size-Sieving of Gaseous C8 , C6 and C3 Hydrocarbon Pairs

Selective separation of industrial important C8 , C6 and C3 hydrocarbon pairs by physisorbents can greatly reduce the energy intensity related to the currently used cryogenic distillation techniques. The achievement of size-sieving based on carbonaceous materials is desirable, but commonly hindered by the random structure of carbons often with a broad pore size distribution. Herein, a pH-regulated pre-condensation strategy was introduced to control the carbon pore architecture by the sp2 /sp3 hybridization of precursor. The lower pH value during pre-condensation of glucose facilitates the growth of aromatic nanodomains, rearrangement of stacked layers and a concomitant transition from sp3 -C to sp2 -C. The subsequent pyrolysis endows the pore size manipulated from 6.8 to 4.8 Å and narrowly distributed over a range of 0.2 Å. The refined pores enable effective size-sieving of C8 , C6 and C3 hydrocarbon pairs with high separation factor of 1.9 and 4.9 for C8 xylene (X) isomers para-X/meta-X and para-X/ortho-X, respectively, 5.1 for C6 alkane isomers n-hexane/3-methylpentane, and 22.0 for C3 H6 /C3 H8 . The excellent separation performance based-on size exclusion effect is validated by static adsorption isotherms and dynamic breakthrough experiments. This synthesis strategy provides a means of exploring advanced carbonaceous materials with controlled hybridized structure and pore sizes for challenging separation needs.

Application of Thermal Response Measurements to Investigate Enhanced Water Adsorption Kinetics in Ball-Milled C2 N-Type Materials

Sorption-based water capture is an attractive solution to provide potable water in arid regions. Heteroatom-decorated microporous carbons with hydrophilic character are promising candidates for water adsorption at low humidity, but the strong affinity between the polar carbon pore walls and water molecules can hinder the water transport within the narrow pore system. To reduce the limitations of mass transfer, C2 N-type carbon materials obtained from the thermal condensation of a molecular hexaazatriphenylene-hexacarbonitrile (HAT-CN) precursor were treated mechanochemically via ball milling. Scanning electron microscopy as well as static light scattering reveal that large pristine C2 N-type particles were split up to a smaller size after ball milling, thus increasing the pore accessibility which consequently leads to faster occupation of the water vapor adsorption sites. The major aim of this work is to demonstrate the applicability of thermal response measurements to track these enhanced kinetics of water adsorption. The adsorption rate constant of a C2 N material condensed at 700 °C remarkably increased from 0.026 s-1 to 0.036 s-1 upon ball milling, while maintaining remarkably high water vapor capacity. This work confirms the advantages of small particle sizes in ultramicroporous materials on their vapor adsorption kinetics. It is demonstrated that thermal response measurements are a valuable and time-saving method to investigate water adsorption kinetics, capacities, and cycling stability.