Proposal Title

Si/C/TiO2 Composite Nanofibers Prepared Using a Sulfur-Templating Method for Lithium Ion Batteries

Primary Faculty Mentor’s Name

Dr. Ji Wu

Proposal Track

Student

Session Format

Poster

Abstract

Presently, lithium Ion Batteries (LIBs) are widely viewed as an optimal candidate for green energy storage and all-electric vehicles. To meet the challenging goals demanded by the above mentioned applications, several obstacles have to be overcome, including lowering the cost, increasing the capacity, enhancing the rate and cycling performance and improving the safety. Nowadays, nanotechnology is playing a critically important role in the advancement of high performance LIBs due to its excellent mechanical properties and huge specific surface area. In this work, silicon nanoparticles (SiNP) of high specific capacity are confined within the structurally stable titanium dioxide nanofiber (TiO2 NF) matrix to improve its electrochemical performance. Si/C/TiO2 composite nanofibers were fabricated using an electrospinning method, followed by a carbonization in helium gas at 800 oC for 4 hrs. Sulfur was employed as a template to facilitate the formation of void structure, thus providing space to the large volume expansion of silicon during lithiation process and mitigate pulverization of silicon particles. Carbonized nanofibers containing TiO2 and Si nanoparticles were also prepared for comparison. The structure, morphology, phase and composition of these nanofibers were characterized using Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, and thermogravimetric analyzer. Carbonized nanofibers containing TiO2 showed a low but stable specific capacity of 105 mAh g-1 after 100 cycles at a current density of 0.09 A g-1. Carbonized nanofibers containing silicon nanoparticles demonstrated an initially high but fast degrading capacity, which is only 73 mAh g-1 after 100 cycles. In contrast, the capacity of silicon in SiNP/C/TiO2 nanofibers prepared using a sulfur-templating method is ~ 3459 mAh g-1 at the fourth cycle, 52 % of which can be maintained after 80 cycles. It is believed that sulfur is functioning as a template to help the formation of void between silicon nanoparticles and TiO2, thus allowing for the ~300% volume change during Si lithiation and delithiation process.

Keywords

Lithium-ion batteries, Silicon nanoparticles, Titanium oxide, Sulfur templating, electrospin

Location

Concourse/Atrium

Presentation Year

2014

Start Date

11-15-2014 9:40 AM

End Date

11-15-2014 10:55 AM

Publication Type and Release Option

Presentation (Open Access)

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Nov 15th, 9:40 AM Nov 15th, 10:55 AM

Si/C/TiO2 Composite Nanofibers Prepared Using a Sulfur-Templating Method for Lithium Ion Batteries

Concourse/Atrium

Presently, lithium Ion Batteries (LIBs) are widely viewed as an optimal candidate for green energy storage and all-electric vehicles. To meet the challenging goals demanded by the above mentioned applications, several obstacles have to be overcome, including lowering the cost, increasing the capacity, enhancing the rate and cycling performance and improving the safety. Nowadays, nanotechnology is playing a critically important role in the advancement of high performance LIBs due to its excellent mechanical properties and huge specific surface area. In this work, silicon nanoparticles (SiNP) of high specific capacity are confined within the structurally stable titanium dioxide nanofiber (TiO2 NF) matrix to improve its electrochemical performance. Si/C/TiO2 composite nanofibers were fabricated using an electrospinning method, followed by a carbonization in helium gas at 800 oC for 4 hrs. Sulfur was employed as a template to facilitate the formation of void structure, thus providing space to the large volume expansion of silicon during lithiation process and mitigate pulverization of silicon particles. Carbonized nanofibers containing TiO2 and Si nanoparticles were also prepared for comparison. The structure, morphology, phase and composition of these nanofibers were characterized using Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, and thermogravimetric analyzer. Carbonized nanofibers containing TiO2 showed a low but stable specific capacity of 105 mAh g-1 after 100 cycles at a current density of 0.09 A g-1. Carbonized nanofibers containing silicon nanoparticles demonstrated an initially high but fast degrading capacity, which is only 73 mAh g-1 after 100 cycles. In contrast, the capacity of silicon in SiNP/C/TiO2 nanofibers prepared using a sulfur-templating method is ~ 3459 mAh g-1 at the fourth cycle, 52 % of which can be maintained after 80 cycles. It is believed that sulfur is functioning as a template to help the formation of void between silicon nanoparticles and TiO2, thus allowing for the ~300% volume change during Si lithiation and delithiation process.