Hot-Chemistry Structural Phase Transformation in Single-Crystal Chalcogenides for Long-Life Lithium Ion Batteries.

Tuned chalcogenide single crystals rooted in sulfur-doped graphene were prepared by high-temperature solution chemistry. We present a facile route to synthesize a rod-on-sheet-like nanohybrid as an active anode material and demonstrate its superior performance in lithium ion batteries (LIBs). This nanohybrid contains a nanoassembly of one-dimensional (1D) single-crystalline, orthorhombic SnS onto two-dimensional (2D) sulfur-doped graphene. The 1D nanoscaled SnS with the rodlike single-crystalline structure possesses improved transport properties compared to its 2D hexagonal platelike SnS2. Furthermore, we blend this hybrid chalcogenide with biodegradable polymer composite using water as a solvent. Upon drying, the electrodes were subjected to heating in vacuum at 150 °C to induce polymer condensation via formation of carboxylate groups to produce a mechanically robust anode. The LIB using the as-developed anode material can deliver a high volumetric capacity of ∼2350 mA h cm-3 and exhibit superior cycle stability over 1500 cycles as well as a high capacity retention of 85% at a 1 C rate. The excellent battery performance combined with the simplistic, scalable, and green chemistry approach renders this anode material as a very promising candidate for LIB applications.

Evidence of covalent synergy in silicon-sulfur-graphene yielding highly efficient and long-life lithium-ion batteries.

Silicon has the potential to revolutionize the energy storage capacities of lithium-ion batteries to meet the ever increasing power demands of next generation technologies. To avoid the operational stability problems of silicon-based anodes, we propose synergistic physicochemical alteration of electrode structures during their design. This capitalizes on covalent interaction of Si nanoparticles with sulfur-doped graphene and with cyclized polyacrylonitrile to provide a robust nanoarchitecture. This hierarchical structure stabilized the solid electrolyte interphase leading to superior reversible capacity of over 1,000 mAh g(-1) for 2,275 cycles at 2 A g(-1). Furthermore, the nanoarchitectured design lowered the contact of the electrolyte to the electrode leading to not only high coulombic efficiency of 99.9% but also maintaining high stability even with high electrode loading associated with 3.4 mAh cm(-2). The excellent performance combined with the simplistic, scalable and non-hazardous approach render the process as a very promising candidate for Li-ion battery technology.

Synthesis of amine functionalized cellulose nanocrystals: optimization and characterization.

A simple protocol was used to prepare amine functionalized cellulose nanocrystals (CNC-NH2). In the first step, epichlorohydrin (EPH) was reacted with ammonium hydroxide to produce 2-hydroxy-3-chloro propylamine (HCPA). In the next step, HCPA was grafted to CNC using the etherification reaction in an organic solution media. Various reaction parameters, such as time, temperature, and reactant molar ratio were performed to determine the optimal reaction conditions. The final product (CNC-NH2(T)) was dialyzed for a week. Further purification via centrifugation yielded the sediment (CNC-NH2(P)) and supernatant (POLY-NH2). The presence of amine groups on the surface of modified CNC was confirmed by FTIR and the amine content was determined by potentiometric titration and elemental analysis. A high amine content of 2.2 and 0.6 mmol amine/g was achieved for CNC-NH2(T) and CNC-NH2(P), respectively. Zeta potential measurements confirmed the charge reversal of amine CNC from positive to negative when the pH was increased from 3 to 10. The flocculation of amine functionalized CNC due to its interactions with a negatively charged surfactant namely, sodium dodecyl sulfate (SDS) was investigated at pH 4. It showed promising results for applications, such as in flocculation of fine dispersions in water treatment. This simple and versatile synthetic method to produce high amine content CNC can be used for further conjugation as required for various applications.

Subeutectic growth of single-crystal silicon nanowires grown on and wrapped with graphene nanosheets: high-performance anode material for lithium-ion battery.

A novel one-pot synthesis for the subeutectic growth of (111) oriented Si nanowires on an in situ formed nickel nanoparticle catalyst prepared from an inexpensive nickel nitrate precursor is developed. Additionally, anchoring the nickel nanoparticles to a simultaneously reduced graphene oxide support created synergy between the individual components of the c-SiNW-G composite, which greatly improved the reversible charge capacity and it is retention at high current density when applied as an anode for a Li-ion battery. The c-SiNW-G electrodes for Li-ion battery achieved excellent high-rate performance, producing a stable reversible capacity of 550 mAh g(-1) after 100 cycles at 6.8 A g(-1) (78% of that at 0.1 A g(-1)). Thus, with further development this process creates an important building block for a new wave of low-cost silicon nanowire materials and a promising avenue for high rate Li-ion batteries.