Date of Award
January 2023
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemical Engineering
First Advisor
Michael Mann
Second Advisor
Xiaodong Hou
Abstract
The increasing demand for high-performance energy storage devices has driven extensive research into developing advanced lithium-ion batteries (LIBs) for various applications, including electric vehicles, portable electronics, and grid energy storage. Anode materials play a critical role in determining the overall performance of LIBs. In this dissertation, the investigation of silicon-based anode materials synthesis, characterization, and electrochemical performance was conducted for high-performance lithium-ion battery (LIB) applications. Four projects (Chapter 3 through 6) will be included in this dissertation. Chapter one includes the background and motivation of developing high-performance anode material for LIBs, followed by the hypothesis, scope of work, and significance of this dissertation. Chapter 2 includes the approach used in this dissertation. Chapter 3 focuses on addressing the challenges of silicon-based anodes for LIBs by synthesizing a porous 3D humic acid-derived graphene and micron-sized silicon composite anode (Si@G foam). Raman spectra confirm the in-situ formation of graphene and Scanning Electron Microscopy (SEM) images show the 3D structure with silicon particles evenly distributed. The Si@G composite-anode exhibits excellent reversible capacity, high-rate capability, and outstanding cycling stability. It displayed a reversible capacity of approximately 656 mAh/g at a current density of 50 mA/g, and a high-rate capability of approximately 433 mAh/g at a current density of 800 mA/g with cycling stability approximately 90% capacity retention after 300 cycles. The graphene foam structure serves as an electrical conductor for the active materials and volume expansion support for silicon particles during the charge/discharge cycle for LIBs, offering potential for advanced silicon-based anodes in high-performance LIBs. Chapter 4 explores the optimization of SiOx/graphite anode design for industrial LIBs applications using the Taguchi method. This method evaluates the effects of conductive agent-to-binder ratio, conductive agents’ combination, and binders’ combination. The optimal factors resulted in a significant improvement in the anode's electrochemical performance, with an Initial coulombic efficiency (ICE) of 88% and an initial de-lithiation capacity of 439 mAh/g. After 400 cycles, the anode achieved 90% rotation. The Taguchi design method is validated by electrochemical kinetic analysis, demonstrating its usefulness in optimizing SiOx/graphite anodes for LIBs. The application of graphene coatings enhances the usability of SiO anodes by improving electronic conductivity and mitigating volume expansion. Chapter 5 investigates the use of non-woven carbon fiber substrates as current collectors for electrodes in high-energy density LIBs. Non-woven carbon fiber substrates offer structural stability, mechanical strength, and high electrical conductivity, which enables efficient electron transfer and better withstands volume changes during cycling. The study shows that non-woven carbon fiber substrates outperform traditional copper/aluminum current collectors in energy density. The energy density of the anode was increased by 70%, and the energy density of the cathode increased by 23%. The study found that anodes and cathodes using non-woven carbon fiber substrates exhibited higher specific capacity densities compared to those using traditional copper/aluminum current collectors. While the ICE needs improvement, non-woven carbon fiber substrates show exciting potential for enhancing LIB electrochemical performance. Chapter 6 explores the use of chemical pre-lithiation to improve the electrochemical performance of the SiOx/graphite composite anodes for LIBs, especially for the ICE. The ICE increased from 88% to 98% using an aryl lithium reagent impregnation method, and the anode's energy density, rate capability, and cycling performance were significantly enhanced. Pre-lithiation methods are promising for improving LIB performance by increasing initial reversible capacity, initiating volume pre-expansion, and creating a synthetic solid electrolyte interface (SEI). SEM imaging with osmium tetroxide staining showed a stable SEI layer after pre-lithiation and cycling tests. Based on the results, the pre-lithiation process for the anode could be used in the industrial process for LIBs anode production. In summary, this dissertation focuses on the silicon-based composite anode materials’ synthesis, characterization, and electrochemical performance evaluation, as well as the implementation of a pre-lithiation technique, provides valuable insights for the development of high-performance anodes for LIBs. The promising results obtained from the SiOx and graphite composite anodes, combined with the benefits of pre-lithiation, display the potential of these materials for enhancing the overall performance of LIBs. The findings of this research will serve as a valuable resource for the research field, battery manufacturers, and engineering work on the development of next-generation LIBs.
Recommended Citation
Zhang, Xin, "The Design And Preparation Of High-Performance Silicon/Carbon Composite Anode For Lithium-Ion Batteries" (2023). Theses and Dissertations. 5277.
https://commons.und.edu/theses/5277