Functional Polymers for Lithium Metal Batteries

Abstract

Lithium metal anode based rechargeable batteries (LMB) are regarded as the most viable alternative to replace state-of-the-art lithium ion batteries (LIB) as they can provide higher-energydensity energy storage. With this year’s Nobel Prize in Chemistry being awarded to Akira Yoshino,M. Stanley Whittingham, and John B. Goodenough for their contribution in developing LIBs, even more attention is now drawn to the development of LMBs. Due to the highly reactive nature of metallic lithium and the change with regard to cathode, electrolyte and anode design, the industrial success of LMB has yet to be achieved. Traditionally, in an LMB the role of polymeric componentsis mostly limited to the role of separators and cathode binders. However, with the continued development of polymer chemistry and its growing number of applications in materials science, it is now recognized that designing and applying functional polymers can greatly improve thepractical performance of an LMB. This thesis describes how various polymer materials could be synthesized and tailored for improving the cycling stability of LMBs. Chapter 1 will systematically discuss the state-of-the-art of various macromolecular approaches to improve each major component of an LMB, namely the electrolyte/separators, anode-electrolyte interface, anode, cathode-electrolyte interface and highenergy- density cathode materials including layered metal oxides and sulfur. Chapter 2 describes the development of two polymer electrolytes with high lithium transference number prepared byatom transfer radical polymerization (ATRP) and anionic ring opening polymerization (ROP). Chapter 3 describes the development of two polymer based artificial solid electrolyte interface (SEI) that can stabilize the lithium deposition on the anode surface during lithium plating. One of the examples uses an organic/inorganic hybrid material prepared by covalently grafting polymers from a solid metal oxide by surface-initiated ATRP. Another one uses a single-ion polymer discussed in Chapter 2. Chapter 4 discusses the development of a composite lithium metal anodethat exhibits flowable properties and is compatible with ceramic solid electrolytes. Chapter 5 discusses how polymeric materials could be used as reactive surfactants to tailor the morphology of lithium metal from plain foils to microparticles and nanoflakes. Finally, a summary with outlook on future directions is provided.