Ag Modified SnS2 Monolayer as a Potential Sensing Material for C4F7N Decompositions: A Density Functional Theory Study.

As the field of 2D materials rapidly evolves, substances such as graphene, metal dichalcogenides, MXenes, and MBenes have garnered extensive attention from scholars in the gas sensing domain due to their unique and superior properties. Based on first-principles calculations, this work explored the adsorption characteristics of both intrinsic and silver (Ag) doped tin disulfide (SnS2) toward the decomposition components of the insulating medium C4F7N (namely, CF4, C3F6, and COF2), encompassing the adsorption energy, charge transfer, density of state (DOS), band structure, and adsorption stability. The results indicated that Ag-doped SnS2 exhibited an effective and stable adsorption for C3F6 and COF2, whereas its adsorption for CF4 was comparatively weaker. Additionally, the potential for Ag-SnS2 in detecting C3F6 was highlighted, inferred from the contributions of the band gap variations. This research provides theoretical guidance for the application of Ag-SnS2 as a sensing material in assessing the operational status of gas-insulated equipment.

Reduced graphene oxide-encaged submicron-silicon anode interfacially stabilized by Al2O3 nanoparticles for efficient lithium-ion batteries.

Silicon-carbon composites have been recognized as some of the most promising anode candidates for advancing new-generation lithium-ion batteries (LIBs). The development of high-efficiency silicon/graphene anodes through a simple and cost-effective preparation route is significant. Herein, by using micron silicon as raw material, we designed a mesoporous composite of silicon/alumina/reduced graphene oxide (Si/Al2O3/RGO) via a two-step ball milling combined annealing process. Commercial Al2O3 nanoparticles are introduced as an interlayer due to the toughening effect, while RGO nanosheets serve as a conductive and elastic coating to protect active submicron silicon particles during lithium alloying/dealloying reactions. Owing to the rational porous structure and dual protection strategy, the core/shell structured Si/Al2O3/RGO composite is efficient for Li+ storage and demonstrates improved electrical conductivity, accelerated charge transfer and electrolyte diffusion, and especially high structural stability upon charge/discharge cycling. As a consequence, Si/Al2O3/RGO yields a high discharge capacity of 852 mA h g-1 under a current density of 500 mA g-1 even after 200 cycles, exhibiting a high capacity retention of ∼85%. Besides, Si/Al2O3/RGO achieves excellent cycling reversibility and superb high-rate capability with a stable specific capacity of 405 mA h g-1 at 3000 mA g-1. Results demonstrate that the Al2O3 interlayer is synergistic with the indispensable RGO nanosheet shells, affording more buffer space for silicon cores to alleviate the mechanical expansion and thus stabilizing active silicon species during charge/discharge cycles. This work provides an alternative low-cost approach to achieving high-capacity silicon/carbon composites for high-performance LIBs.

Generation Characteristics of Solid Byproducts of the C4F7N-CO2-O2 Gas Mixture under PD Fault.

With the gradual improvement of the requirements for the safe and stable operation of gas-insulated equipment (GIE), the eco-friendly insulating gas C4F7N-CO2-O2 has become the best choice to replace SF6 and apply it to various medium-voltage (MV) and high-voltage (HV) GIE. At present, the generation characteristics of solid decomposition products of the C4F7N-CO2-O2 gas mixture under partial discharge (PD) fault need to be studied. In this paper, a 96 h PD decomposition test was carried out by simulating metal protrusion defects in GIE with needle-plate electrodes to study the generation characteristics of C4F7N-CO2-O2 gas mixture solid decomposition products under PD fault and their compatibility with metal conductors. It was found that obvious ring-shaped solid precipitates appeared in the central area of the surface of the plate electrode under the action of long-term PD, mainly including metal oxides (CuO), silicates (CuSiO3), fluorides (CuF, CFX), carbon oxides (CO, CO2), and nitrogen oxides (NO, NO2). The addition of 4% O2 has little effect on the element composition and valence state of PD solid precipitates, but it can reduce their yield to a certain extent. The corrosion effect of O2 in the gas mixture on metal conductors is weaker than that of C4F7N.

Compatibility and Interaction Mechanism between the C4F7N/CO2/O2 Gas Mixture and FKM and NBR.

The C4F7N/CO2/O2 gas mixture received a great deal of attention for its potential use in eco-friendly gas-insulated equipment (GIE). The evaluation of the compatibility between C4F7N/CO2/O2 and sealing rubber is necessary and significant considering the high working pressure (0.14-0.6 MPa) of GIE. Herein, we explored the compatibility between C4F7N/CO2/O2 and fluororubber (FKM) and nitrile butadiene rubber (NBR) for the first time by analyzing the gas components, rubber morphology, elemental composition, and mechanical properties. The interaction mechanism of the gas-rubber interface was further investigated based on the density functional theory. We found that C4F7N/CO2/O2 is compatible with FKM and NBR at 85 °C, while the surface morphology changed at 100 °C, with white granular and agglomerated lumps appearing on FKM and multi-layer flakes being generated on NBR. The accumulation of the fluorine element occurred, and the compressive mechanical properties of NBR deteriorated after the gas-solid rubber interaction. Overall, the compatibility between FKM and C4F7N/CO2/O2 is superior, which could be employed as the sealing material for C4F7N-based GIE.