Compatibility of Graphite Materials with Block Copolymer Electrolyte for Lithium Batteries

• Other Authors: Zhou, Sifei (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Chemical engineering
• Online Access: http://purl.flvc.org/fsu/fd/FSU_FA2016_Zhou_fsu_0071N_13603

Graphite has good lifetime and rate capability in liquid electrolyte-based batteries and supercapacitors. Meanwhile, the polymer electrolyte have been considered as a promising technology for battery applications for its safety and flexible cell configuration design which satisfy the requirements of stand-by power and electric vehicles(EV). It is commonly recognized that graphite and PEO-based polymer electrolyte have poor compatibility due to high interfacial resistance and co-intercalation phenomenon. However, it was reported recently that high molecular weight PEO electrolyte along with material processing approaches to graphite materials result in improved compatibility. Motivated by this finding, it is reasonable to expect that further improvements in battery performance can be gained with block compolymer that has mechanical properties sufficient to maintain electrode structure. Therefore, a high molecular weight block copolymer (polystyrene-b-PEO) was used to replace PEO as polymer electrolyte in this study. In addition, the block copolymer has better mechanical properties that improve both thermal and mechanical stability of the cell or might even partially reduce the complicated engineering techniques apply to the graphite material. In this study, the compatibility of two different graphite materials with block copolymer were investigated by using detailed analysis of electrochemical methods that include galvanostatic cycling (GCPL) and electrochemical impedance spectroscopy (EIS). In particular, EIS was used to examine the formation of the solid electrolyte interphase (SEI) on the graphite surface which has significant impact on the cycling performance of the cell. It is concluded that SEI formation in the first few cycles on flake graphite appears to be much more stable than on MCMB leading to better capacity retention. Flake graphite materials have a better compatibility with block copolymer (SEO) comparing to MCMB graphite supported by better cycling performance and electrode-electrolyte interphase property. === A Thesis submitted to the Department of Chemical and Biomedical Engineering in partial fulfillment of the requirements for the degree of Master of Science. === Fall Semester 2016. === November 8, 2016. === block copolymer, Lithium battery, SEI === Includes bibliographical references. === Daniel Hallinan, Professor Directing Thesis; Jingjiao Guan, Committee Member; Ravindran Chella, Committee Member; Jianping Zheng, Committee Member.