Batteries for electrical energy storage have become ubiquitous in a world of portable and mobile electronics. However, current lithium-ion battery technology suffers from several key limitations, such as, high cost, limited energy storage density, poor durability, and severe environmental impact. These shortcomings limit the viability of many important emerging technologies, such as electric vehicles and off-peak storage for renewable energy generation systems. Batteries based on a lithium-sulphur (Li-S) chemistry can theoretically achieve energy densities six times greater than conventional lithium-ion (Li-ion) batteries but have typical lifetimes of only 100 recharge cycles. This award studies new approaches to the manufacture of electrodes for lithium-sulphur batteries that have long lifespan and are affordable. Preliminary results have demonstrated that a battery cathode can be manufactured by high temperature carbonization of wheat dough creating a porous carbon network. The resulting carbon foam structure is covered with carbon nanotubes, which enables a dense loading of sulphur nanoparticles to increase energy capacity. The porous carbon/carbon nanotube scaffold structure prevents the degradation of the active sulphur material, extending the durability of the battery to over 4000 cycles. The battery components are assembled through a scalable, continuous, and high-throughput process from low-cost precursors, which also contributes to improved environmental sustainability. This research develops new paradigms for design and nanomanufacturing of energy storage devices. These research advances are disseminated to K-12, undergraduate, and graduate students, as well as the general public through targeted courses, seminars, and publications.
The research objective of the project is to address key technological and engineering barriers to achieving high-throughput manufacturing of batteries with exceptionally high energy and power densities and ultra-long lifespan. The approach is to derive electrode materials from a readily available, low cost, environmentally-benign material, specifically, wheat dough. The project addresses research gaps such as severe capacity degradation, incomplete sulfur utilization, and the severe 'shuttle effect' of dissolvable intermediates during the electrochemical reaction process. Research activities feature a systems-level focus spanning (1) synthesis of the mesoporous activated carbon/carbon nanotube scaffolds, (2) roll-to-roll manufacturing of the developed cathode into Li-S batteries, and (3) structural and mechanical characterization of electrode materials to evaluate the role of structure on battery degradation. The primary contributions of this work are to improve the effective conductivity of the sulphur cathode by embedding sulphur nanoparticles within a highly-conductive activated carbon/carbon nanotube scaffold and to study how the structure impedes electrode degradation by inhibiting the 'shuttle effect' and limiting reaction volume changes. The fundamental mechanism of the one-step synthesis of carbon nanotubes on carbonized yeast from wheat dough is determined. A prototype automated roll-to-roll manufacturing process is devised to produce high-performance Li-S batteries.