Anton Kovalchuk

SnO2-reduced graphene oxide nanoribbons as anodes for lithium ion batteries with enhanced cycling stability

A nanocomposite material of SnO2-reduced graphene oxide nanoribbons has been developed. In this composite, the reduced graphene oxide nanoribbons are uniformly coated by nanosized SnO2 that formed a thin layer of SnO2 on the surface. When used as anodes in lithium ion batteries, the composite shows outstanding electrochemical performance with the high reversible discharge capacity of 1,027 mAh/g at 0.1 A/g after 165 cycles and 640 mAh/g at 3.0 A/g after 160 cycles with current rates varying from 0.1 to 3.0 A/g and no capacity decay after 600 cycles compared to the second cycle at a current density of 1.0 A/g. The high reversible capacity, good rate performance and excellent cycling stability of the composite are due to the synergistic combination of electrically conductive reduced graphene oxide nanoribbons and SnO2. The method developed here is practical for the large-scale development of anode materials for lithium ion batteries.

Luminescent Polymer Composite Films Containing Coal-Derived Graphene Quantum Dots

Luminescent polymer composite materials, based on poly(vinyl alcohol) (PVA), as a matrix polymer and graphene quantum dots (GQDs) derived from coal, were prepared by casting from aqueous solutions. The coal-derived GQDs impart fluorescent properties to the polymer matrix, and the fabricated composite films exhibit solid state fluorescence. Optical, thermal, and fluorescent properties of the PVA/GQD nanocomposites have been studied. High optical transparency of the composite films (78 to 91%) and excellent dispersion of the nanoparticles are observed at GQD concentrations from 1 to 5 wt %. The maximum intensity of materials photoluminescence has been achieved at 10 wt % GQD content. These materials could be used in light emitting diodes (LEDs), flexible electronic displays, and other optoelectronic applications.

Tin Disulfide Nanoplates on Graphene Nanoribbons for Full Lithium Ion Batteries.

A nanocomposite material made of layered tin disulfide (SnS2) nanoplates vertically grown on reduced graphene oxide nanoribbons (rGONRs) has been successfully developed as an anode in lithium ion batteries by a facile method. At a rate of 0.4 A/g, the material exhibits a high discharge capacity of 823 mAh/g even after 800 cycles. It shows excellent rate stability when the current density varies from 0.1 to 3.0 A/g with a Coulombic efficiency larger than 99%. In order to demonstrate the anode material for practical applications, SnS2-rGONR/LiCoO2 full cells were constructed. To the best of our knowledge, this is the first time that a full cell has been successfully developed using metal chalcogenides as an anode. The full cell delivers a high capacity of 642 mAh/g at 0.2 A/g, superior rate, and cycling stability after long-term cycling. Moreover, the full cell has a high output working voltage of 3.4 V. These excellent lithium storage performances in half and full cells can be mainly attributed to the synergistic effect between the highly conductive network of rGONRs and the high lithium-ion storage capability of layered SnS2 nanoplates.

Sandwich structured graphene-wrapped FeS-graphene nanoribbons with improved cycling stability for lithium ion batteries

Sandwich structured graphene-wrapped FeS-graphene nanoribbons (G@FeS-GNRs) were developed. In this composite, FeS nanoparticles were sandwiched between graphene and graphene nanoribbons. When used as anodes in lithium ion batteries (LIBs), the G@FeS-GNR composite demonstrated an outstanding electrochemical performance. This composite showed high reversible capacity, good rate performance, and enhanced cycling stability owing to the synergy between the electrically conductive graphene, graphene nanoribbons, and FeS. The design concept developed here opens up a new avenue for constructing anodes with improved electrochemical stability for LIBs.

Microwave Heating of Functionalized Graphene Nanoribbons in Thermoset Polymers for Wellbore Reinforcement.

Here, we introduce a systematic strategy to prepare composite materials for wellbore reinforcement using graphene nanoribbons (GNRs) in a thermoset polymer irradiated by microwaves. We show that microwave absorption by GNRs functionalized with poly(propylene oxide) (PPO-GNRs) cured the composite by reaching 200 °C under 30 W of microwave power. Nanoscale PPO-GNRs diffuse deep inside porous sandstone and dramatically enhance the mechanics of the entire structure via effective reinforcement. The bulk and the local mechanical properties measured by compression and nanoindentation mechanical tests, respectively, reveal that microwave heating of PPO-GNRs and direct polymeric curing are major reasons for this significant reinforcement effect.

Tuning Electrical Conductivity of Inorganic Minerals with Carbon Nanomaterials.

Conductive powders based on Barite or calcium carbonate with chemically converted graphene (CCG) were successfully synthesized by adsorption of graphene oxide (GO) or graphene oxide nanoribbons (GONRs) onto the mineral surfaces and subsequent chemical reduction with hydrazine. The efficient adsorption of GO or GONRs on the surface of Barite and calcium carbonate-based mineral particles results in graphene-wrapped hybrid materials that demonstrate a concentration dependent electrical conductivity that increases with the GO or GONR loading.