Battery and Fuel Cell Technology

Development of rechargeable batteries with high performance and safety is one of the key challenges faced by modern electrochemistry. Rechargeable Li-ion batteries attracted significant attention during the last two decades due to their widespread application in portable electronics, medical implants, grid-level energy storage and electric vehicles. Recently, secondary Na-ion batteries emerged as an alternative candidate for large scale energy storage. Low-cost and abundance of resources are main advantages of this technology. Li-O2 batteries are another high-performance battery system, which has several fold energy densities compared to the conventional Li-ion batteries. Despite of the several advantages of Li and Naion based batteries, their energy and power densities are not sufficient for more energy demanding commercial applications such as long-range driving. Consequently, development of high-performance electrode materials is necessary to improve the energy and power density of these secondary battery systems. Nanostructured transition metal oxide based electrodes are fabricated to mitigate the drawbacks of electrodes used in conventional Li and Na-ion batteries. Main focus of this work is the interface and defect engineering to boost pseudocapacitive type Li/Na ion storage. Solution based bottom-up synthetic approach and carbothermal reduction method are used for the synthesis of defect and interface engineered electrode materials. Lithium and sodium ion batteries containing defect engineered 1D, 2D and 3D electrodes demonstrated specific capacities up to 1300 mAh/g and high rate performance up to 30 A/g current density. Spectroscopic, microscopic and electrochemical studies proved conventional conversion reaction and pseudocapacitive Li/Na ion storage. High specific capacity (5000 mAh/g) and stable cycling are observed in the case of Li-O2 batteries. Enhanced electrochemical performances are attributed to the synergy between pseudocapacitive and conversion-type charge storage mechanism.