Theses and Dissertations

Date of Award

5-2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Dr. Mataz Alcoutlabi

Second Advisor

Dr. Horacio Vasquez

Third Advisor

Dr. Javier Ortega

Abstract

The work presented in this thesis focuses on the processing, characterization, and electrochemical results of centrifugally spun composite carbon fiber electrodes for application as anode material in lithium-ion batteries. The work is presented as a compilation of two major projects. First, the use of novel Co3O4 wet coatings to increase the capacity of carbon fibers produced from Polyacrylonitrile (PAN). In this work, PAN fibers are produced via the Forcespinning method, and were heat treated by oxidation in air at 200 °C for four hours, and subsequent carbonization at 600 °C for six hours. The electrochemical performance of the Co3O4/C composite-fiber anode with different active material loading was evaluated by using galvanostatic charge/discharge, rate performance, cyclic voltammetry, and electrochemical impedance spectroscopy experiments. The CCF anode delivered a specific charge capacity of 632 and 420 mAh g–1 after 100 cycles at 100 and 200 mAg–1, respectively, and exhibited good rate capability.

This work is then followed by the electrochemical performance of silicon nanoparticles imbedded in fiber composites derived from polyvinylpyrrolidone (PVP), and their enhanced cyclability when using Sodium Carboxymethyl Cellulose (Na-CMC) polymer coating. The composite anodes were fabricated via a similar sol-gel synthesis method, however, annealing of Si/PVP fibers was done at low temperature (160 °C), and carbonization was carried out under inert gas to prevent further oxidation of the silicon nanoparticles in the PVP fibers. The silicon/ carbon fiber composites, together with Na-CMC delivered a specific capacity of 2300 mAhg-1 for the first 20 cycles and showed an initial columbic efficiency of 83% when tested in a standard lithium electrolyte with FEC as additive. The positive effect of Na-CMC coating on the carbon fiber/ silicon composite was seen in the diminished loss of capacity in the first cycle by up to 20%. These results suggest that Na-CMC/ CMC structures can enhance the cyclability and stable SEI formation of centrifugally spun carbon fiber composites.

Comments

Copyright 2021 Jonathan Ayala. All Rights Reserved.

https://go.openathens.net/redirector/utrgv.edu?url=https://www.proquest.com/dissertations-theses/novel-coating-methods-on-centrifugally-spun/docview/2572580324/se-2?accountid=7119

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