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Yunya Zhang1 Xiaodong Li1

1, Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia, United States

Considering the irreversible environmental damages and the huge cost induced by fossil fuel consumption and Co/graphite mining, it is environmentally and socially significant to produce energy storage devices from low cost and renewable materials. In order to achieve lightweight, mechanical robustness, and various functionalities, nature often constructs hierarchically porous structures or thin films. These delicate structures, if well utilized, can largely improve the performances of energy storage devices. Thusly, a rational design strategy is to derive high-performance electrodes from biomass materials. Banana peels, as the inedible part of the most popular fruit, have a typical porous structure. After treated by NiNO3, the micron sized pores on activated banana peel (ABP) effectively enhanced the accessibly of electrolyte, nanopores immobilized and encapsulated polysulfides, and graphene coated Ni nanoparticles improved conductivity, leading to a high specific capacity of the assembled Li-S batteries. To increase the utilization efficiency of graphene, graphene oxide sheets were incorporated with activated paper carbon (APC) via capillary method. Thin graphene layer were coated around cellulose fibers with nano sized bulges and wrinkles, which not only increased sulfur loading, but also encapsulated polysulfides and buffer volume fluctuations, rendering an ultra-long lifespan of 1000 cycles with over 60 % capacity retention rate of Li-S batteries. In addition to optimize the performance of biomass derived electrodes, we also seek holistic utilization of biomass materials. An all-solid, flexible supercapacitor was fabricated from a whole egg. Eggshell was used as templates and egg white/yolk was employed as carbon source for 2D graphene like carbon films. Solid electrolyte was produced by egg white/yolk and KOH. Egg shell membrane was then used as separator. The assembled supercapacitors exhibited superior performances.

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