Hamed Hosseini Bay

Scalable Synthesis of Nano-Silicon from Beach Sand for Long Cycle Life Li-ion Batteries

Herein, porous nano-silicon has been synthesized via a highly scalable heat scavenger-assisted magnesiothermic reduction of beach sand. This environmentally benign, highly abundant, and low cost SiO2 source allows for production of nano-silicon at the industry level with excellent electrochemical performance as an anode material for Li-ion batteries. The addition of NaCl, as an effective heat scavenger for the highly exothermic magnesium reduction process, promotes the formation of an interconnected 3D network of nano-silicon with a thickness of 8-10 nm. Carbon coated nano-silicon electrodes achieve remarkable electrochemical performance with a capacity of 1024 mAhg−1 at 2 Ag−1 after 1000 cycles.

Stable Cycling of SiO2 Nanotubes as High-Performance Anodes for Lithium-Ion Batteries

Herein, SiO2 nanotubes have been fabricated via a facile two step hard-template growth method and evaluated as an anode for Li-ion batteries. SiO2 nanotubes exhibit a highly stable reversible capacity of 1266 mAhg−1 after 100 cycles with negligible capacity fading. SiO2 NT anodes experience a capacity increase throughout the first 80 cycles through Si phase growth via SiO2 reduction. The hollow morphology of the SiO2 nanotubes accommodates the large volume expansion experienced by Si-based anodes during lithiation and promotes preservation of the solid electrolyte interphase layer. The thin walls of the SiO2 nanotubes allow for effective reduction in Li-ion diffusion path distance and, thus, afford a favorable rate cyclability. The high aspect ratio character of these nanotubes allow for a relatively scalable fabrication method of nanoscale SiO2-based anodes.

Stable Cycling of SiO 2 Nanotubes as High-Performance Anodes for Lithium-Ion Batteries

Herein, SiO2 nanotubes have been fabricated via a facile two step hard-template growth method and evaluated as an anode for Li-ion batteries. SiO2 nanotubes exhibit a highly stable reversible capacity of 1266 mAhg−1 after 100 cycles with negligible capacity fading. SiO2 NT anodes experience a capacity increase throughout the first 80 cycles through Si phase growth via SiO2 reduction. The hollow morphology of the SiO2 nanotubes accommodates the large volume expansion experienced by Si-based anodes during lithiation and promotes preservation of the solid electrolyte interphase layer. The thin walls of the SiO2 nanotubes allow for effective reduction in Li-ion diffusion path distance and, thus, afford a favorable rate cyclability. The high aspect ratio character of these nanotubes allow for a relatively scalable fabrication method of nanoscale SiO2-based anodes.

Monodisperse Porous Silicon Spheres as Anode Materials for Lithium Ion Batteries

Highly monodisperse porous silicon nanospheres (MPSSs) are synthesized via a simple and scalable hydrolysis process with subsequent surface-protected magnesiothermic reduction. The spherical nature of the MPSSs allows for a homogenous stress-strain distribution within the structure during lithiation and delithiation, which dramatically improves the electrochemical stability. To fully extract the real performance of the MPSSs, carbon nanotubes (CNTs) were added to enhance the electronic conductivity within the composite electrode structure, which has been verified to be an effective way to improve the rate and cycling performance of anodes based on nano-Si. The Li-ion battery (LIB) anodes based on MPSSs demonstrate a high reversible capacity of 3105 mAh g−1. In particular, reversible Li storage capacities above 1500 mAh g−1 were maintained after 500 cycles at a high rate of C/2. We believe this innovative approach for synthesizing porous Si-based LIB anode materials by using surface-protected magnesiothermic reduction can be readily applied to other types of SiOx nano/microstructures.

Silicon decorated cone shaped carbon nanotube clusters for lithium ion battery anodes.

In this work, we report the synthesis of an three-dimensional (3D) cone-shape CNT clusters (CCC) via chemical vapor deposition (CVD) with subsequent inductively coupled plasma (ICP) treatment. An innovative silicon decorated cone-shape CNT clusters (SCCC) is prepared by simply depositing amorphous silicon onto CCC via magnetron sputtering. The seamless connection between silicon decorated CNT cones and graphene facilitates the charge transfer in the system and suggests a binder-free technique of preparing lithium ion battery (LIB) anodes. Lithium ion batteries based on this novel 3D SCCC architecture demonstrates high reversible capacity of 1954 mAh g(-1) and excellent cycling stability (>1200 mAh g(-1) capacity with ≈ 100% coulombic efficiency after 230 cycles).

Towards Scalable Binderless Electrodes: Carbon Coated Silicon Nanofiber Paper via Mg Reduction of Electrospun SiO2 Nanofibers

The need for more energy dense and scalable Li-ion battery electrodes has become increasingly pressing with the ushering in of more powerful portable electronics and electric vehicles (EVs) requiring substantially longer range capabilities. Herein, we report on the first synthesis of nano-silicon paper electrodes synthesized via magnesiothermic reduction of electrospun SiO2 nanofiber paper produced by an in situ acid catalyzed polymerization of tetraethyl orthosilicate (TEOS) in-flight. Free-standing carbon-coated Si nanofiber binderless electrodes produce a capacity of 802 mAh g−1 after 659 cycles with a Coulombic efficiency of 99.9%, which outperforms conventionally used slurry-prepared graphite anodes by over two times on an active material basis. Silicon nanofiber paper anodes offer a completely binder-free and Cu current collector-free approach to electrode fabrication with a silicon weight percent in excess of 80%. The absence of conductive powder additives, metallic current collectors, and polymer binders in addition to the high weight percent silicon all contribute to significantly increasing capacity at the cell level.

Scalable Multifunctional Ultra-thin Graphite Sponge: Free-standing, Superporous, Superhydrophobic, Oleophilic Architecture with Ferromagnetic Properties for Environmental Cleaning.

Water decontamination and oil/water separation are principal motives in the surge to develop novel means for sustainability. In this prospect, supplying clean water for the ecosystems is as important as the recovery of the oil spills since the supplies are scarce. Inspired to design an engineering material which not only serves this purpose, but can also be altered for other applications to preserve natural resources, a facile template-free process is suggested to fabricate a superporous, superhydrophobic ultra-thin graphite sponge. Moreover, the process is designed to be inexpensive and scalable. The fabricated sponge can be used to clean up different types of oil, organic solvents, toxic and corrosive contaminants. This versatile microstructure can retain its functionality even when pulverized. The sponge is applicable for targeted sorption and collection due to its ferromagnetic properties. We hope that such a cost-effective process can be embraced and implemented widely.

Fluorescence quenching metrology of graphene

We investigate the application of fluorescence quenching microscopy (FQM) for visual characterization of graphene quality, number of layers and uniformity over its landscape. The method relies on the fact that pristine, modified and multi-layer graphene regions quench fluorescence with different rates. Steady-state and time-resolved emission spectroscopy are used to comparatively characterize the photophysical behavior of pristine graphene relative to unquenched dye on bare substrate. The results demonstrate that with premeditated choice of Fluorescence dye, the interaction between fluorophores and graphene provides valuable tools for identifying the chemical structure and thickness of graphene. Fluorescence quenching metrology can be implemented as the basis for a microscopy based metrology for 2D materials.