Development of anode materials for high-performance lithium rechargeable batteries

Abstract

The principal challenge for human being in the 21st century is to secure sustainability and renewabil-ity in respect to energy, environment, and natural resources. In this context, high capacity, high performance and renewable electricity storage devices have been required for advanced electric vehicles and new regenera-tion energy resources. Silicon (Si) has been considered as a promising candidate for high-capacity anode ma-terial. Si can form Li22Si5 during lithiation, which have extraordinary high theoretical capacity (4200 mAh g-1). However, the volume expansion of Si by up to 300% during lithiation poses a big obstruction to commerciali-zation. In chapter 1, the factors for high-performance binder was investigated to solve this intrinsic problem of Si. It showed that the interactions, such as covalent bonding and supramolecular interaction, between pol-ymer chains are very important. Self-healing effect of polymeric binder was especially critical for longevity. In chapter 2, for the sake of synergetic effects of covalent and supramolecular interactions, we examined β-cyclodextrin polymeric binder which has covalent bonding effect via hyperbranched structure and consider-able hydroxyl groups as hydrogen bonding sites. In chapter 3, we inspected organic anode material for re-newable lithium-ion batteries. Although many electrochemical organic compounds were reported in the early studies, the researches on carbonyl-type anode material have been recently reported. We proposed the meth-od to decrease the redox potential of the high-voltage organic material by attaching electron-donor to car-bonyl redox centers. Furthermore, the low solubility attributed to the increase in the hydrophilicity by elec-tron-donor enables the good capacity retention.