Novel gel polymer electrolytes based on electrospun poly(vinylidene fluoride)-poly (ethylene oxide) (PVdF-PEO) polymer blend for lithium Ion batteries

• Main Author: Chow, Kency.
• Other Authors: Srinivasan Madhavi
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Materials::Energy materials
• Online Access: http://hdl.handle.net/10356/48835
• Institution: Nanyang Technological University

Energy issues are central to discussions regarding the long-terms sustainability of current global needs. The need to harvest, transmit and store energy to meet global demands is some of the biggest problem we will face in the near future. Higher density energy storage devices are constantly required. From cars to pocket mobile phones, there will be an increasing need to improve energy conversion and increase storage capacity. Many investigations had been made to improve the power of the cathode and anode of lithium-ion battery (LIB) while the separator, which is a critical component, is often overlooked and neglected. In the recent years, synthetic polymers have been tailored as electron or ion conductors, when combined with appropriate liquid electrolyte it forms a gel polymer electrolyte and their ionic conductivity can be put to use. Polyethylene oxide (PEO) is added into poly(vinylidene fluoriade) (PVdF), and the blends are very promising in this field. The membrane was prepared by electrospinning the polymer mixture in solvent. The addition of PEO and controlling electrospinning parameters would improve and enhance certain properties of the polymer electrolyte membrane like the porosity and its pore size, which leads to a better electrolyte uptake, hence better ionic conductivity. Gel polymer electrolytes (GPE) based on PEO will be our research area. The study will investigate the usage of different liquid in the PVdF-PEO (90:10) blend polymer matrix, namely Li-TFSI, Li-ClO4, Li-PF6, Li-BF4 and Li-CF3SO3, would enhance the performance of the cell. The GPE are prepared by soaking the electrospun polymer membrane into the liquid electrolyte and then assembled into a cell with Li/LiFePO4 cathode. The ionic conductivity and interfacial resistance of the different cells are studied and based on those, the evaluation of the discharge properties, cycle properties and capacity fade are investigated. This report will discuss the synthesis and characterization of the electrospun membrane based on PVdF-PEO (90:10) blend, and the activating the fibrous membranes with different liquid electrolyte, leading to different ionic conductivity and interfacial resistance of the different cells. Then, evaluation of the electrochemical properties and cell performance of these electrolytes would be discussed. The Li-TFSI based GPE is found to be the best with the highest cycle performance with high initial discharge properties and low capacity fade after continuous cycling.