Engineering topics
Das, Pratyusha
Publications and source records attributed to Das, Pratyusha.
Development of design strategies for conjugated polymer binders in lithium-ion batteries
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The Role of Functionalized Conducting Polymer Binders in Improving Power Density and Cycle Life of Lithium-Sulfur Batteries
Lithium-Sulfur batteries are promising as the next-generation of low-cost, high-energy rechargeable batteries. However, the commercialization of this battery has been limited by poor rate capability and cycle life. To improve the performance of Li-S cells, we have investigated the role of two n-dopable conducting polymers, N2200 and N2200-OE, as binders for the sulfur cathode. The electron and ion transport properties of these polymer binders, along with their strong affinity for polysulfides, results in significantly enhanced performance compared to cells with the traditional insulating PVDF binder. The role of these conducting polymer binders in enhancing the performance of the cells is analyzed using impedance spectroscopy, shuttle current measurements, conductivity measurements, UV–vis spectroscopy, GIWAXS studies and post-cycling analysis of the anodes. The conducting polymer binders reduce the cell impedance by a factor of four leading to a marked improvement in rate capability. The shuttling of the polysulfides and the formation of insoluble sulfides at the anode is curtailed by the interaction of the polysulfides with the backbone of the polymer binders, leading to an impressive capacity retention of 82% after 500 cycles. These studies demonstrate the benefit of tailored polymer binders at the sulfur electrode in addressing the limitations of lithium-sulfur batteries.
Understanding the Role of π-Conjugated Polymers as Binders in Enabling Designs for High-Energy/High-Rate Lithium Metal Batteries
Developing lithium-ion batteries with both high specific energy and high-power capability is a challenging task because of the necessity for meeting conflicting design requirements. We show that high-energy and high-rate capability can be achieved by using various π -conjugated p-dopable polymers as binders at the cathode and by lowering the mass fraction of all the inactive components of the cell. We report a lithium-metal battery that can deliver 320 Wh kg −1 at C/2 using a mass-efficient cell design. To this end, three conducting polymers with different ionic and electronic conductivities have been studied; dihexyl-substituted poly(3,4-propylenedioxythiophene) (PProDOT-Hx 2 ), poly(3-hexylthiophene) (P3HT), and a new Random Copolymer (Hex:OE)(80:20) PProDOT. These conducting polymers are compared against a conventional polymer binder, PVDF. We show that under the mass-efficient conditions required for achieving high specific energy and rate capability, the conducting polymers play a crucial role by providing electronic and ionic conductivity, protection against rapid growth of solid electrolyte interphase (SEI), and access to a large electrochemically active surface area. Thus, the use of conducting polymers with appropriate molecular structure as binders opens a viable pathway to maximizing the specific energy and rate capability of lithium-ion battery cathodes.