Advanced Materials for Rechargeable Lithium Batteries

Doctoral thesis, 2012

Lithium rechargeable batteries have gained much attention in the pursuit for alternative energy sources because of advantages such as high energy density and high electric potential. In addition, the development of low-cost materials has been of interest to reduce the cost of batteries, especially those destined for transportation applications such as electric (EVs) or hybrid-electric vehicles (HEVs). At the same time, safety is a growing concern together with increasing environmental requirements. Moreover, research on light and flexible batteries has also been intensive, motivated by their potential applications in minute electronic systems. The development of new materials is a key to meet the challenges faced by battery technology. An ionic liquid-based polymer electrolyte could reduce the risk of explosion with non-flammability and high thermal stability. The use of LiMPO4 cathodes contributes with high thermal stability as a result of the covalent bond between metal and oxygen. Organic electrodes provide flexibility and may facilitate recycling of rechargeable lithium batteries. In this study, these materials have been employed for ultra-safe, flexible, green and high-rate-capability lithium batteries. Raman, XPS, DSC, and dielectric spectroscopy were used to investigate their physical properties, and the electrochemical performance of the ionic liquid-based polymer electrolytes are explored in combination with some LiMPO4 cathodes. The ion coordination, ionic conductivity, oxidation stability, dissolution of electrode material, and electrochemical properties were investigated. A new nano-fibrous organic radical polymer [(poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA)]   electrode, a new organic cathode material 2,3,6,7,10,11-hexamethoxytriphenylene (HMTP) containing methoxy functional group (CH3O) and Py14TFSI-based polymer electrolyte to overcome the drawback of organic electrode materials such as high amount of carbon and dissolution of active materials has also been investigated.