Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
An effective strategy to tackle the twin crises of global deforestation and fossil fuel depletion is to recycle bio-mass materials for energy storage devices. Batteries have been proven to be the most effective electrochemical energy conversion and storage devices. As the most widely used battery system, lithium-ion (Li-ion) batteries have served our daily life and changed the world extensively in the past two decades. However, the potential of Li-ion battery system is approaching its limit and unable to fulfill diverse requirements. Among all possible candidates, lithium sulfur (Li-S) battery chemistry is considered to be one of the most promising next-generation, high energy density battery chemistries. The theoretical gravimetric capacity of this reaction is 1675 mAh g-1, and with the expected average voltage during discharge, the maximum energy density can be 2600 mWh g-1. However, how to build high-capacity and long-life span Li-S batteries via accessible and scalable methods is still questionable. Here we report a unique and innovative solution to capitalize on a currently overlooked resource to produce high-performance lithium-sulfur (Li-S) batteries from recycled paper. Common paper hardboard was peeled into long stripes and integrated with graphene oxide (GO) sheets by a capillary absorption method. The paper/GO hybrid was then activated at high temperature, forming activated paper carbon (APC)/graphene scaffold. The capillary absorbed GO sheets were homogeneously coated on the APC fibers and shrined geometrically during heating, forming nano sized bulges and pores, which remarkably improved sulfur loading and cathode conductivity. The recycled paper derived graphene Li-S battery exhibited superior life span of 620 cycles with an excellent capacity retention rate of 60.5%. More importantly, the APC/graphene/S stayed integral without pulverization even after such long cycling, indicating excellent mechanical robustness of cathode material. Since the malfunction of the battery can be ascribed to the anode, an activated paper carbon (APC) interlayer was sandwiched between the Li anode and the separator to suppress the degradation of Li anode by protecting the Li from unfavorable reactions, stretching the battery lifespan up to 980 cycles with a capacitance retention rate of 52.3% and improved rate ability. The capillary adsorption method and the porous anode interlayer configuration should find more applications in other porous bio-mass materials for energy storage devices.