ChBE Seminar Series: Vibha Kalra
Tuesday, October 28, 2014
11:00 a.m.-12:15 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
Professor Jeffery Klauda
Freestanding Nanofiber Electrodes for Supercapacitors and Batteries
Department of Chemical and Biomolecular Engineering
Dr. Kalra will also host a graduate school information session from 3:30–4:30 p.m. in the ChBE conference room (2113A Chemical and Nuclear Engineering Building).
Fabrication of novel three-dimensional material architectures is essential for development of energy storage devices that allow high rate operation with sufficient energy capacity. In this talk, I will present our work on development of freestanding nanofiber-based electrodes using a simple electrospinning methodology for application in supercapacitors (EDLC/Pseudocapacitors) and lithium-based (Li-S/Li-O2) batteries. I will also briefly talk about our work on molecular dynamics (MD) simulations to understand the effect of elongational flow, a key characteristic of electrospinning, on assembly within phase separating polymer blends – a material system relevant to the fabrication of nanofiber electrodes.
We have developed porous carbon nanofibers (PCNF) that exhibit specific surface area of >1500 m2/g and multi-levels of pore sizes in the range of micro (< 2 nm), meso (< 50 nm) and macropores (> 50 nm). We studied these materials as freestanding electrodes in electric double layer capacitors (EDLC) (with aqueous and ionic liquid electrolytes) and as platform for polyanilene (PANi) deposition to develop hybrid supercapacitors that integrate electric double layer and pseudocapacitive energy storage. The unique combination of pores at different length scales allows us to achieve a battery-like energy density of up to 80 Wh/kg, while retaining high power and cycle life in EDLCs. In-operando infrared spectroelectrochemistry was conducted to understand the transport of ions through the carbon electrode pores and its effect on performance in ionic liquid-based EDLCs. In the hybrid supercapacitor devices, we demonstrated that the PCNF mats retain their EDLC behavior post PANi coating providing excellent electrochemical performance. We also investigated the use of nanofiber materials for battery devices – Li-S, Li- O2 and redox flow batteries. In particular, for Li-S battery devices, we demonstrated a facile methodology to localize soluble polysulfides that results in a high initial discharge capacity and capacity retention during cycling.
About the Speaker
Vibha Kalra is an assistant professor in the Department of Chemical and Biological Engineering at Drexel University. Prof. Kalra received her BS degree from Indian Institute of Technology, Delhi, India in 2004 and Ph.D. from Cornell University in 2009, both in Chemical Engineering. Prior to joining Drexel in the Fall of 2010, she worked at Intel Corporation in the electronic packaging research division. Prof. Kalra is an associate editor of Chemical Engineering Science Journal (since Sept. 2013). She is a recipient of several awards including the Drexel career development award (2011), NSF CAREER award (2012), ONR summer faculty fellowship award (2013) and the ECS early career travel award (2014).