DEVELOPMENT AND FABRICATION OF PROTEINS AS MULTIFUNCTIONAL MATERIALS FOR ENERGY STORAGE APPLICATIONS

Xuewei Fu

Safe and high-energy batteries are the ultimate goal of development trends for advanced energy storage devices. Realization of this goal demands for developing (i) high-performance solid electrolytes for substituting today’s flammable liquid electrolytes, and (ii) high-capacity electrodes capable of storing more energy than current electrodes. In this dissertation, proteins have been exploited for achieving above two objectives. This dissertation includes four parts. The first part Introduction describes the overview of lithium-based batteries and the development trends. The second part including Chapters 2, 3 and 4, provide studies on utilizing protein for advanced solid polymer electrolytes (SPEs). In Chapter 2, a novel protein-based solid electrolyte is fabricated, and the unique ion-conduction mechanism is analyzed. Different from conventional SPEs, the protein-based solid electrolyte reveals a unique decoupled ion-conduction mechanism. In Chapters 3 and 4, composite electrolytes enhanced by protein/TiO2 hybrid nanofillers are studied. Two types of hybrid nanofillers are fabricated: protein/TiO2 nanoparticles (Chapter 3) and protein/TiO2 nanowires (Chapter 4). Chapter 3 mainly discusses the proper way for manipulating protein configuration by TiO2 nanoparticles and concludes that a favorable protein configuration benefits transport of lithium ions. Chapter 4 outlines the study of core-shell protein/TiO2 nanowires for further improving the electrolyte properties. Adding these two hybrid nanofillers into polyethylene oxide (PEO) electrolytes, the physicochemical, mechanical and electrochemical properties are improved. Protein/TiO2 nanowire system shows further improvement compared with the nanoparticle counterpart. In the third part (Chapter 5 and 6), to address the critical issues of high-capacity sulfur cathodes, proteins are adopted for binder materials and battery interlayers. In Chapter 5, a protein-based binder with abilities of buffering large volume change of sulfur, adsorbing polysulfides and promoting electrochemical reactions is studied. These advantages warrant high loading sulfur cathodes and excellent battery performance. In Chapter 6, a unique interlayer (protein nanofilter) is fabricated, and the rational porous structure and surface properties of the nanofilter enable strong binding with polysulfides. Consequently, the electrochemical performance of the Li-S batteries is enhanced. In the last part, Chapter 7, the critical conclusions drawn from the studies are summarized and the outlook is proposed.

DEVELOPMENT AND FABRICATION OF PROTEINS AS MULTIFUNCTIONAL MATERIALS FOR ENERGY STORAGE APPLICATIONS

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