Electrochemical studies of hexavanadates and lithium manganese oxides for aqueous rechargeable lithium batteries

• Main Author: Nair, Vivek Sahadevan
• Other Authors: Srinivasan Madhavi
• Format: Theses and Dissertations
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/66326
• Institution: Nanyang Technological University

Aqueous rechargeable lithium ion battery(ARLB) systems are potential alternative to existing rechargeable battery systems like Ni-Cd, Ni-MH, lead acid and lithium ion battery due to its advantages including rate capabilities, safety and environmental friendliness. Investigations of high energy/power, long cycle life and low-cost materials for aqueous rechargeable lithium ion batteries are of great interest especially for transportation applications such as electric (EVs) or hybrid-electric vehicles (HEVs), large-scale power storage grids and wearable electronics. ARLBs have higher power density but lower energy densities compared to lithium polymer batteries. ARLBs have much better rate capabilities (10-5000mAg-1) compared to lithium ion batteries (0.1-10mAg-1). This thesis focuses on the development and study of novel hexavanadate based anode and lithium manganese oxide based cathode materials for ARLBs with higher energy densities and better cycle life performances at higher rates. In this thesis, new set of hexavanadate based materials with high theoretical capacities like Li3V6O16, Na2V6O16, K2V6O16, CaV6O16 and SrV6O16 from the family of metal vanadium oxides for aqueous rechargeable lithium ion battery were synthesized by both facile hydrothermal and sol-gel method using Vanadium Oxide (V2O5) and hydroxide salt of the alkali metal ion (LiOH, NaOH, KOH, Ca(OH)2 and Sr(OH)2. Similarly, different morphologies of high-voltage Spinel materials like LiMn2O4 were explored for its suitability to develop a better full cell ARLB. Electrochemical studies show higher lithium ion insertion into hexavandates but with irreversible capacity loss which is the research challenge this work has aimed to study and tried to address. As-prepared material were subjected to crystallographic X-ray diffraction (XRD analysis, mechanical properties, surface morphology {field emission scanning electron microscope (FE-SEM) and transmission electron microscopy (TEM)} characterization to evaluate the effect of crystal structure and morphology on its electrochemical performance. CaV6O16 doped with TiO2 as anode exhibits an initial capacity of 350mAhg-1 and retention of 200mAhg-1 over 100 charge/discharge cycles, at a current density of 500mAg-1, which is much better than any aqueous lithium-ion battery reported. LiMn2O4 hollow microspheres as cathode displays an initial capacity of 145mAhg-1 and a capacity retention of more than 90% of its initial capacity for over 1000 cycles at a current density of 500mAhg-1, which proves its potential for usage in commercial applications. Fundamental studies on the importance of different morphologies, mechanism of intercalation/de-intercalation of lithium ions in aqueous media into hexavanadtes, dissolution of electrode material, effect of electrolyte’s counter-ion on rate performance, influence of annealing temperature on crystallinity and electrochemical performance were conducted to help us optimize several parameters to achieve the best performance. Further, a full-cell ARLB is constructed in a pouch cell configuration using LiMn2O4 as cathode and Na2V6O16 and CaV6O16 as Anode and evaluated for its electrochemical performance. Additionally, different energy harvesting options are explored to power a combination of two or more energy storage systems coupled to a sensor-driven smart consumption system. Finally, we demonstrate the application of an intelligent power sourcing storage and consumption system (IPSSC) through two case-studies using an ontology developed with the knowledge obtained through proper classification of the available energy harvesting systems, energy requirement of devices and their components and ambient real-time source of energy. A kinetic energy harvesting based RMS simulation tool was used to calculate the number of data packets that could be transmitted in a wireless sensor network application from the above real-time energy sources.