Renewable Energy Global Innovations features: Silicon-Multi-Walled Carbon Nanotubes-Carbon Microspherical Composite as High-Performance Anode for Lithium-Ion Batteries

Significance Statement

Researchers have been facing the challenge of increasing better performance of storage devices in order to meet up with the required demands for the future. Their investigations are mostly based on obtaining the most appropriate electrode materials.

In view of having a better performance of lithium-ion batteries, electrode materials such as anode and cathode are major factors that need to be considered as they contribute effectively to enhancement of energy density of these batteries. Required features for anode materials include high capacity, high cyclability, high coulombic efficiencyand the excellent rate performance amongst others.

From previous research, silicon when used as anode materials shows certain attractive attributes. However, their poor cyclability remains a bane to their advantages as it often leads to pulverization due to the huge volume change over repeated cycles.

Researchers later discovered that silicon nanoparticles when used as an anode in lithium-ion batteries exhibits high cyclability, but the morphological bindings of these nanoparticles and their connection towards current collector during lithiation-delithiation process still remains a challenge that needs to be overcome.

A new research led by Professor Jinbao Zhao at Xiamen University in China involved the fabrication of silicon-multi-walled carbon nanotubes-carbon (Si- MWNTS-C) microspheres via ball milling and spray drying method by a carbonization process for the latter in view of analyzing their performance towards enhancement of lithium-ion batteries. The work was published in Journal of Materials Science.

They characterized the features of the fabricated silicon-multi-walled carbon nanotubes-carbon with the aid of scanning electron microscopy, transmission electron and x-ray diffraction coupled with electrochemical measurements with the aid of cyclic voltammetry and electrochemical impedance spectra.

Results from the characterization techniques confirmed carbon as the effective conductive agent between silicon nanoparticles and the multi-wall carbon nanotubes microspheres which provides a 3D conductive network thereby resulting to a high electrical conductivity. They also possessed good porosity which makes them adapt to large changes in volume during discharge-charge process.

At a current density of 0.2 Ag^-1, the authors observed while using the ball-milling method that the specific capacity of the silicon-multi-walled carbon nanotubes-carbon to be 1100 m Ah g^-1 while also possessing high capacity retention of about 90% after 60 cycles. This was not the case for the ordinary silicon nanoparticles as it showed drastic reduction after 50 cycles. Further results also confirmed an enhanced columbic efficiency which was also found when using the spray drying method. The silicon-multi-walled carbon nanotubes-carbon also possessed high rate performance and reversibility when observed at current densities range from 0.1 to 0.6 A g^-1.

In order to test the performance of the silicon-multi-walled carbon nanotubes-carbon in a lithium-ion battery, LiCoO₂ was used as the cathode. A high cyclic stability was still observed and no morphological changes were observed when viewed after 100 cycles except for growth spherical particles.

The authors of the study provided an improved performance for silicon nanoparticles with the aid of multi-walled carbon conductor link, which shows a potential improvement for lithium-ion batteries.

Reference

Zhang, Y., Li, K., Ji, P., Chen, D., Zeng, j., Sun, Y., Zhang, P., Zhao, J. Silicon-Multi-Walled Carbon Nanotubes-Carbon Microspherical Composite as High-Performance Anode for Lithium-Ion Batteries, Journal of Materials Science 52 (2017) 3630-3641.

Go To Journal of Materials Science  Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)

Renewable Energy Global Innovations features: Enhanced Oil Recovery (EOR) Using Nanoparticle Dispersions: Underlying Mechanism and Imbibition Experiments

Significance Statement

Nanofluids have become attractive agents for EOR recently. Higher ultimate oil recovery has been reported previously by using nanofluids. The two major mechanisms reported in literature in achieving this feature include: The reduction of interfacial tension between the aqueous phase and oil phase, and the rock wettability alteration. Despite recently widely conducted research using a nanofluid for EOR, the underlying operating mechanism of recovery by a nanofluid is still not well understood.

A new approach which makes use of nanofluids for displacement of oil from solid substrate by nanoparticle structuring leads to structural disjoining pressure which separates oil from the solid substrate. Other factors such as combination of nanoparticle formulation, contact angle and capillary pressure are also known to influence the separation of oil from substrate.

Researchers from Illinois Institute of Technology at Chicago presented results of imbibition experiments using a silica nanofluid and an Illinois Institute of Technology (IIT) nanofluid that displaces crude oil from Berea sandstone and single-glass capillaries. The researchers developed a nanoparticle formulation in view of surviving at a high-salinity environment containing calcium and magnesium ions accompanied with study of structural disjoining pressure mechanism for crude oil displacement. The work was published in peer-reviewed journal, Energy & Fuels.

Through imbibition test, 55% of the crude oil was recovered using the silica nanofluid, compared to only 2% recovered with the pH 9.7 DI water after 15 days. At an increased temperature of 55 ^oC, the IIT nanofluid displaced crude oil approximately 50% from Berea sandstone compared with 17% by the brine solution.

For the mechanistic study, the researchers observed rapid shrinkage of contact region after introduction of brine and the position of contact region didn’t change with time after wedge region was formed, hence oil drop was not detached. However, for the nanofluid case, a new contact line (inner contact line) appears and spreads due to nanoparticles ordering in the oil/solid/aqueous three phase contact region after the wedge film formed. This confirms the structural disjoining pressure mechanism. It is the first time that this mechanism of crude oil displacement from a solid substrate is demonstrated experimentally.

The authors finally conducted model studies of crude oil displacement using single glass capillaries to directly visualize the crude oil displacement process from inside the pore. Around 60% crude oil was displaced by IIT nanofluid compared to 3% in the brine. Moreover, the authors were able to show from their results that the IIT nanofluid thrives in harsh saline environment where silica nanoparticles cannot.

 

About The Author

Hua Zhang is a Ph.D. Student in the Chemical and Biological Department at Illinois Institute since 2011. He received his B.S. and M.S. degrees in Chemical Engineering from Beijing University of Chemical Technology, China in 2008 and 2011 respectively.

His research area lies in wetting and spreading of nanofluids on solid substrate; dynamics of liquids in the capillary; surface cleaning and enhanced oil recovery using nanofluids.  

Journal Reference

Hua Zhang, Alex Nikolov, Darsh Wasan.  Enhanced Oil Recovery (EOR) Using Nanoparticle Dispersions: Underlying Mechanism and Imbibition Experiments, Energy Fuels 28 (2014) 3002-3009.

Department of Chemical and Biological Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States.

 

Go To Energy Fuels   Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)