Keywords

Aqueous process, soluble, adhesive, electrolyte, binder, lithium batteries

Abstract

This dissertation describes a new vinyl-acrylic copolymer that displays great potential for applications in lithium ion batteries by enabling processes that are novel, faster, safer, and less costly than existing manufacturing methods. Overall, the works presented are based on tailored chemical synthesis directly applied to lithium ion battery manufacturing. Current manufacturing methods still have many flaws such as toxic processes and other time consuming if not costly steps. Understanding the chemistry of materials and processes related to battery manufacturing allows the design of techniques and methods that can ultimately improve the performance of existing batteries while reducing the cost. Chapter 1 provides an introduction to lithium batteries in terms of energy output, standard electrode and electrolyte materials, and processes for fabricating battery components. In this chapter, slightly more emphasis is placed on the electrolyte aspects of lithium battery technology, namely the plasticization of gel polymer hosts by liquid electrolyte and the standalone solid polymer electrolytes. Chapter 2 focuses on the free radical polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA), methyl methacrylate (MMA), and isobutyl vinyl ether (IBVE) monomers to afford a vinyl-acrylic poly(PEGMA-co-MMA-co-IBVE) random copolymer and its detailed properties as a soluble, amorphous, and adhesive electrolyte that is able to permanently hold 800 times its own weight. Such material properties envision a printable battery manufacturing procedure, since existing electrolytes lack adhesion at a single macromolecular level. Without adhesion, the cathode and anode layers easily delaminate from the cell assembly, not to mention weak interfacial contact and poor mass transfer with the electrolyte. Many soft matter type electrolytes have been reported, but they lack either adhesive strength or ease of solubility. Obtaining both properties in iv a single material is a rarity. Chapter 3 aims at improving the ionic conductivity of the poly(PEGMA-co-MMA-co-IBVE) copolymer electrolyte by studying the effect of internal and external plasticizers, molecular weight of PEGMA monomer, and addition of inorganic solid state electrolytes. The inorganic electrolyte additives include Li(1+x+y)AlxTi(2-x)SiyP(3-y)O12, LiILi2WO4 mixture, Li7La3Zr2O12, and Li2S-P2S5 as part of an organic-inorganic hybrid approach. Electrolytes can also be used as an electrode binder so long as it has structural integrity and allows ion transfer to and from the active electrode material during insertion/extraction processes. In Chapter 4, the use of this electrolyte as a water-soluble binder for the aqueous fabrication of LiCoO2 cathodes is presented. Results of this study demonstrated the first aqueous process fabrication of thick, flexible, and fully compressed lithium ion battery electrodes by using commercial nickel foam as a supporting current collector. This feat is rather impressive because these properties are far superior to other aqueous binders in terms of material loading per electrode, specific area capacity, durability, and cell resistance. Finally, Chapter 5 expands on this concept by using the poly(PEGMA-co-MMA-co-IBVE) copolymer for the aqueous fabrication of a low voltage Li4Ti5O12 anode type electrode. Each component of a lithium ion battery serves a distinct role and undergoes unique electrochemical processes during cycling. The fact that this poly(PEGMA-co-MMA-co-IBVE) copolymer can be used in all three components, albeit for only about 50 cycles in a liquid half cell setup, demonstrates as a proof of concept that switching the current toxic manufacturing of lithium-ion batteries to an aqueous process is highly feasible. Furthermore, new electrode manufacturing techniques are also deemed possible. A conclusive summary along with directions for future work concerning the v novelties of this unique multifunctional vinyl-acrylic copolymer as an electrolyte, a cathode binder, and an anode binder are discussed in Chapter 6.

Notes

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Graduation Date

2013

Semester

Spring

Advisor

Zhai, Lei

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Chemistry

Degree Program

Chemistry

Format

application/pdf

Identifier

CFE0004761

URL

http://purl.fcla.edu/fcla/etd/CFE0004761

Language

English

Release Date

May 2013

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

Subjects

Dissertations, Academic -- Sciences, Sciences -- Dissertations, Academic,

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Included in

Chemistry Commons

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